Playlist
  • Journalism student?

    Lessons in security they might not teach at your j-school.

    Journalism school teaches you many things, but it doesn't always cover how to protect yourself from surveillance. Click through to learn how to assess the risks you face and how to protect yourself against them. This playlist will teach you how to understand various threats, communicate safely with others, protect yourself and your data online, and get around Internet censorship.

  • An Introduction to Threat Modeling

    There is no single solution for keeping yourself safe online. Digital security isn’t about which tools you use; rather, it’s about understanding the threats you face and how you can counter those threats. To become more secure, you must determine what you need to protect, and whom you need to protect it from. Threats can change depending on where you’re located, what you’re doing, and whom you’re working with. Therefore, in order to determine what solutions will be best for you, you should conduct a threat modeling assessment.

    When Conducting an Assessment, There are Five Main Questions you Should Ask Yourself: Anchor link

    1. What do you want to protect?
    2. Who do you want to protect it from?
    3. How likely is it that you will need to protect it?
    4. How bad are the consequences if you fail?
    5. How much trouble are you willing to go through in order to try to prevent those?

    When we talk about the first question, we often refer to assets, or the things that you are trying to protect. An asset is something you value and want to protect. When we are talking about digital security, the assets in question are usually information. For example, your emails, contact lists, instant messages, and files are all assets. Your devices are also assets.

    Write down a list of data that you keep, where it’s kept, who has access to it, and what stops others from accessing it.

    In order to answer the second question, “Who do you want to protect it from,” it’s important to understand who might want to target you or your information, or who is your adversary. An adversary is any person or entity that poses a threat against an asset or assets. Examples of potential adversaries are your boss, your government, or a hacker on a public network.

    Make a list of who might want to get ahold of your data or communications. It might be an individual, a government agency, or a corporation.

    A threat is something bad that can happen to an asset. There are numerous ways that an adversary can threaten your data. For example, an adversary can read your private communications as they pass through the network, or they can delete or corrupt your data. An adversary could also disable your access to your own data.

    The motives of adversaries differ widely, as do their attacks. A government trying to prevent the spread of a video showing police violence may be content to simply delete or reduce the availability of that video, whereas a political opponent may wish to gain access to secret content and publish it without you knowing.

    Write down what your adversary might want to do with your private data.

    The capability of your attacker is also an important thing to think about. For example, your mobile phone provider has access to all of your phone records and therefore has the capability to use that data against you. A hacker on an open Wi-Fi network can access your unencrypted communications. Your government might have stronger capabilities.

    A final thing to consider is risk. Risk is the likelihood that a particular threat against a particular asset will actually occur, and goes hand-in-hand with capability. While your mobile phone provider has the capability to access all of your data, the risk of them posting your private data online to harm your reputation is low.

    It is important to distinguish between threats and risks. While a threat is a bad thing that can happen, risk is the likelihood that the threat will occur. For instance, there is a threat that your building might collapse, but the risk of this happening is far greater in San Francisco (where earthquakes are common) than in Stockholm (where they are not).

    Conducting a risk analysis is both a personal and a subjective process; not everyone has the same priorities or views threats in the same way. Many people find certain threats unacceptable no matter what the risk, because the mere presence of the threat at any likelihood is not worth the cost. In other cases, people disregard high risks because they don't view the threat as a problem.

    In a military context, for example, it might be preferable for an asset to be destroyed than for it to fall into enemy hands. Conversely, in many civilian contexts, it's more important for an asset such as email service to be available than confidential.

    Now, Let’s Practice Threat Modeling Anchor link

    If you want to keep your house and possessions safe, here are a few questions you might ask:

    • Should I lock my door?
    • What kind of lock or locks should I invest in?
    • Do I need a more advanced security system?
    • What are the assets in this scenario?
      • The privacy of my home
      • The items inside my home
    • What is the threat?
      • Someone could break in.
    • What is the actual risk of someone breaking in? Is it likely?

    Once you have asked yourself these questions, you are in a position to assess what measures to take. If your possessions are valuable, but the risk of a break-in is low, then you probably won’t want to invest too much money in a lock. On the other hand, if the risk is high, you’ll want to get the best locks on the market, and perhaps even add a security system.

    Last reviewed: 
    2015-01-12
  • Communicating with Others

    Telecommunication networks and the Internet have made communicating with people easier than ever, but have also made surveillance more prevalent than it has ever been in human history. Without taking extra steps to protect your privacy, every phone call, text message, email, instant message, voice over IP (VoIP) call, video chat, and social media message may be vulnerable to eavesdroppers.

    Often the safest way to communicate with others is in person, without computers or phones being involved at all. Because this isn’t always possible, the next best thing is to use end-to-end encryption while communicating over a network if you need to protect the content of your communications.

    How Does End-to-End Encryption Work? Anchor link

    When two people want to communicate securely (for example, Akiko and Boris) they must each generate crypto keys. Before Akiko sends a message to Boris she encrypts it to Boris's key so that only Boris can decrypt it. Then she sends the already-encrypted message across the Internet. If anyone is eavesdropping on Akiko and Boris—even if they have access to the service that Akiko is using to send this message (such as her email account)—they will only see the encrypted data and will be unable read the message. When Boris receives it, he must use his key to decrypt it into a readable message.

    End-to-end encryption involves some effort, but it's the only way that users can verify the security of their communications without having to trust the platform that they're both using. Some services, such as Skype, have claimed to offer end-to-end encryption when it appears that they actually don't. For end-to-end encryption to be secure, users must be able to verify that the crypto key they're encrypting messages to belongs to the people they believe they do. If communications software doesn't have this ability built-in, then any encryption that it might be using can be intercepted by the service provider itself, for instance if a government compels it to.

    You can read Freedom of the Press Foundation's whitepaper, Encryption Works for detailed instructions on using end-to-end encryption to protect instant messages and email. Be sure to check out the following SSD modules as well:

    Voice Calls Anchor link

    When you make a call from a landline or a mobile phone, your call is not end-to-end encrypted. If you're using a mobile phone, your call may be (weakly) encrypted between your handset and the cell phone towers. However as your conversation travels through the phone network, it's vulnerable to interception by your phone company and, by extension, any governments or organizations that have power over your phone company. The easiest way to ensure you have end-to-end encryption on voice conversations is to use VoIP instead.

    Beware! Most popular VoIP providers, such as Skype and Google Hangouts, offer transport encryption so that eavesdroppers cannot listen in, but the providers themselves are still potentially able to listen in. Depending on your threat model, this may or may not be a problem.

    Some services that offer end-to-end encrypted VoIP calls include:

    In order to have end-to-end encrypted VoIP conversations, both parties must be using the same (or compatible) software.

    Text Messages Anchor link

    Standard text (SMS) messages do not offer end-to-end encryption. If you want to send encrypted messages on your phone, consider using encrypted instant messaging software instead of text messages.

    Some end-to-end encrypted instant messaging services use their own protocol. So, for instance, users of Signal on Android and iOS can chat securely with others who use those programs. ChatSecure is a mobile app that encrypts conversations with OTR on any network that uses XMPP, which means you can choose from a range of independent instant messaging services.

    Instant Messages Anchor link

    Off-the-Record (OTR) is an end-to-end encryption protocol for real-time text conversations that can be used on top of a variety of services.

    Some tools that incorporate OTR with instant messaging include:

    Email Anchor link

    Most email providers give you a way of accessing your email using a web browser, such as Firefox or Chrome. Of these providers, most of them provide support for HTTPS, or transport-layer encryption. You can tell that your email provider supports HTTPS if you log in to your webmail and the URL at the top of your browser begins with the letters HTTPS instead of HTTP (for example: https://mail.google.com).

    If your email provider supports HTTPS, but does not do so by default, try replacing HTTP with HTTPS in the URL and refresh the page. If you’d like to make sure that you are always using HTTPS on sites where it is available, download the HTTPS Everywhere browser add-on for Firefox or Chrome.

    Some webmail providers that use HTTPS by default include:

    • Gmail
    • Riseup
    • Yahoo

    Some webmail providers that give you the option of choosing to use HTTPS by default by selecting it in your settings. The most popular service that still does this is Hotmail.

    What does transport-layer encryption do and why might you need it? HTTPS, also referred to as SSL or TLS, encrypts your communications so that it cannot be read by other people on your network. This can include the other people using the same Wi-Fi in an airport or at a café, the other people at your office or school, the administrators at your ISP, malicious hackers, governments, or law enforcement officials. Communications sent over your web browser, including the web pages that you visit and the content of your emails, blog posts, and messages, using HTTP rather than HTTPS are trivial for an attacker to intercept and read.

    HTTPS is the most basic level of encryption for your web browsing that we recommend for everybody. It is as basic as putting on your seat belt when you drive.

    But there are some things that HTTPS does not do. When you send email using HTTPS, your email provider still gets an unencrypted copy of your communication. Governments and law enforcement may be able to access this data with a warrant. In the United States, most email providers have a policy that says they will tell you when you have received a government request for your user data as long as they are legally allowed to do so, but these policies are strictly voluntary, and in many cases providers are legally prevented from informing their users of requests for data. Some email providers, such as Google, Yahoo, and Microsoft, publish transparency reports, detailing the number of government requests for user data they receive, which countries make the requests, and how often the company has complied by turning over data.

    If your threat model includes a government or law enforcement, or you have some other reason for wanting to make sure that your email provider is not able to turn over the contents of your email communications to a third party, you may want to consider using end-to-end encryption for your email communications.

    PGP (or Pretty Good Privacy) is the standard for end-to-end encryption of your email. Used correctly, it offers very strong protections for your communications. For detailed instructions on how to install and use PGP encryption for your email, see:

    What End-To-End Encryption Does Not Do Anchor link

    End-to-end encryption only protects the content of your communication, not the fact of the communication itself. It does not protect your metadata—which is everything else, including the subject line of your email, or who you are communicating with and when.

    Metadata can provide extremely revealing information about you even when the content of your communication remains secret.

    Metadata about your phone calls can give away some very intimate and sensitive information. For example:

    • They know you rang a phone sex service at 2:24 am and spoke for 18 minutes, but they don't know what you talked about.
    • They know you called the suicide prevention hotline from the Golden Gate Bridge, but the topic of the call remains a secret.
    • They know you spoke with an HIV testing service, then your doctor, then your health insurance company in the same hour, but they don't know what was discussed.
    • They know you received a call from the local NRA office while it was having a campaign against gun legislation, and then called your senators and congressional representatives immediately after, but the content of those calls remains safe from government intrusion.
    • They know you called a gynecologist, spoke for a half hour, and then called the local Planned Parenthood's number later that day, but nobody knows what you spoke about.

    If you are calling from a cell phone, information about your location is metadata. In 2009, Green Party politician Malte Spitz sued Deutsche Telekom to force them to hand over six months of Spitz’s phone data, which he made available to a German newspaper. The resulting visualization showed a detailed history of Spitz’s movements.

    Protecting your metadata will require you to use other tools, such as Tor, at the same time as end-to-end encryption.

    For an example of how Tor and HTTPS work together to protect the contents of your communications and your metadata from a variety of potential attackers, you may wish to take a look at this explanation.

    Last reviewed: 
    2017-01-12
  • Creating Strong Passwords

    Because remembering many different passwords is difficult, people often reuse a small number of passwords across many different accounts, sites, and services. Today, users are constantly being asked to come up with new passwords—many people end up reusing the same password dozens or even hundreds of times.

    Reusing passwords is an exceptionally bad security practice, because if an attacker gets hold of one password, she will often try using that password on various accounts belonging to the same person. If that person has reused the same password several times, the attacker will be able to access multiple accounts. That means a given password may be only as secure as the least secure service where it's been used.

    Avoiding password reuse is a valuable security precaution, but you won't be able to remember all your passwords if each one is different. Fortunately, there are software tools to help with this—a password manager (also called a password safe) is a software application that helps store a large number of passwords safely. This makes it practical to avoid using the same password in multiple contexts. The password manager protects all of your passwords with a single master password (or, ideally a passphrasesee discussion below) so you only have to remember one thing. People who use a password manager no longer actually know the passwords for their different accounts; the password manager can handle the entire process of creating and remembering the passwords for them.

    For example, KeePassX is an open source, free password safe that you keep on your desktop. It's important to note that if you're using KeePassX, it will not automatically save changes and additions. This means that if it crashes after you've added some passwords, you can lose them forever. You can change this in the settings.

    Using a password manager also helps you choose strong passwords that are hard for an attacker to guess. This is important too; too often computer users choose short, simple passwords that an attacker can easily guess, including "password1," "12345," a birthdate, or a friend's, spouse's, or pet's name. A password manager can help you create and use a random password without pattern or structure—one that won't be guessable. For example, a password manager is able to choose passwords like "vAeJZ!Q3p$Kdkz/CRHzj0v7,” which a human being would be unlikely to remember—or guess. Don't worry; the password manager can remember these for you!

    Syncing Your Passwords Across Multiple Devices Anchor link

    You may use your passwords on more than one device, such as your computer and your smart phone. Many password managers have a password-synchronizing feature built in. When you sync your password file, it will be up to date on all of your devices, so that if you’ve added a new account on your computer, you will still be able to log into it from your phone. Other password managers will offer to store your passwords “in the cloud,” which is to say, they will store your passwords encrypted on a remote server, and when you need them on a laptop or mobile, they will retrieve and decrypt them for you automatically. Password managers that use their own servers to store or help synchronize your passwords are more convenient, but the trade-off is that they are slightly more vulnerable to attack. If you just keep your passwords on your computer, then someone who can take over your computer may be able to get hold of them. If you keep them in the cloud, your attacker may target that also. It's not usually a compromise you need to worry about unless your attacker has legal powers over the password manager company or is known for targeting companies or internet traffic. If you use a cloud service, the password manager company may also know what services you use, when, and where from.

    Choosing Strong Passwords Anchor link

    There are a few passwords that do need to be memorized and that need to be particularly strong: those that ultimately lock your own data with cryptography. That includes, at least, passwords for your device, encryption like full-disk encryption, and the master password for your password manager.

    Computers are now fast enough to quickly guess passwords shorter than ten or so characters. That means short passwords of any kind, even totally random ones like nQ\m=8*x or !s7e&nUY or gaG5^bG, are not strong enough for use with encryption today.

    There are several ways to create a strong and memorable passphrase; the most straightforward and sure-fire method is Arnold Reinhold's "Diceware."

    Reinhold's method involves rolling physical dice to randomly choose several words from a word list; together, these words will form your passphrase. For disk encryption (and password safe), we recommend selecting a minimum of six words.

    Try making a password using Reinhold’s “Diceware” method.

    When you use a password manager, the security of your passwords and your master password is only as strong as the security of the computer where the password manager is installed and used. If your computer or device is compromised and spyware is installed, the spyware can watch you type your master password and could steal the contents of the password safe. So it's still very important to keep your computer and other devices clean of malicious software when using a password manager.

    A Word About “Security Questions” Anchor link

    Be aware of the “security questions” (such as “What is your mother’s maiden name?” or "What was your first pet's name?") that websites use to confirm your identity if you do forget your password. Honest answers to many security questions are publicly discoverable facts that a determined adversary can easily find, and therefore bypass your password entirely. For instance, US vice-presidential candidate Sarah Palin had her Yahoo! account hacked this way. Instead, give fictional answers that, like your password, no one knows but you. For example, if the password question asks you your pet’s name, you may have posted photos to photo sharing sites with captions such as “Here is a photo of my cute cat, Spot!” Instead of using “Spot” as your password recovery answer, you might choose “Rumplestiltskin.” Do not use the same passwords or security question answers for multiple accounts on different websites or services. You should store your fictional answers in your password safe, too.

    Think of sites where you’ve used security questions. Consider checking your settings and changing your responses.

    Remember to keep a backup of your password safe! If you lose your password safe in a crash (or if you have your devices taken away from you), it may be hard to recover your passwords. Password safe programs will usually have a way to make a separate backup, or you can use your regular backup program.

    You can usually reset your passwords by asking services to send you a password recovery email to your registered email address. For that reason, you may want to memorize the passphrase to this email account also. If you do that, then you will have a way of resetting passwords without depending on your password safe.

    Multi-factor Authentication and One-time Passwords Anchor link

    Many services and software tools let you use two-factor authentication, also called two-step authentication or two-step login. Here the idea is that in order to log in, you need to be in possession of a certain physical object: usually a mobile phone, but, in some versions, a special device called a security token. Using two-factor authentication ensures that even if your password for the service is hacked or stolen, the thief won't be able to log in unless they also have possession or control of a second device and the special codes that only it can create.

    Typically, this means that a thief or hacker would have to control both your laptop and your phone before they have full access to your accounts.

    Because this can only be set up with the cooperation of the service operator, there is no way to do this by yourself if you're using a service that doesn't offer it.

    Two-factor authentication using a mobile phone can be done in two ways: the service can send you an SMS text message to your phone whenever you try to log in (providing an extra security code that you need to type in), or your phone can run an authenticator application that generates security codes from inside the phone itself. This will help protect your account in situations where an attacker has your password but does not have physical access to your mobile phone.

    Some services, such as Google, also allow you to generate a list of one-time passwords, also called single-use passwords. These are meant to be printed or written down on paper and carried with you (although in some cases it might be possible to memorize a small number of them). Each of these passwords works only once, so if one is stolen by spyware when you enter it, the thief won't be able to use it for anything in the future.

    If you or your organization run your own communications infrastructure, such as your own e-mail servers, there's freely available software that can be used to enable two-factor authentication for accessing your systems. Ask your systems administrators to look for software offering implementations of the open standard “Time-Based One-Time Passwords” or RFC 6238.

    Threats of Physical Harm or Imprisonment Anchor link

    Finally, understand that there is always one way that attackers can obtain your password: They can directly threaten you with physical harm or detention. If you fear this may be a possibility, consider ways in which you can hide the existence of the data or device you are password-protecting, rather than trust that you will never hand over the password. One possibility is to maintain at least one account that contains largely unimportant information, whose password you can divulge quickly.

    If you have good reason to believe that someone may threaten you for your passwords, it's good to make sure your devices are configured so that it won't be obvious that the account you are revealing is not the “real” one. Is your real account shown in your computer's login screen, or automatically displayed when you open a browser? If so, you may need to reconfigure things to make your account less obvious.

    In some jurisdictions, such as the United States or Belgium, you may be able to legally challenge a demand for your password. In other jurisdictions, such as the United Kingdom or India, local laws allow the government to demand disclosure. EFF has detailed information for anyone travelling across U.S. borders who wishes to protect their data on their digital devices in our Defending Privacy at the U.S. Border guide.

    Please note that intentional destruction of evidence or obstruction of an investigation can be charged as a separate crime, often with very serious consequences. In some cases, this can be easier for the government to prove and allow for more substantial punishments than the alleged crime originally being investigated.

    Last reviewed: 
    2016-01-13
  • How to: Delete Your Data Securely on Mac OS X

    Most of us think that a file on our computer is deleted once we put the file in our computer's trash folder and empty the trash; in reality, deleting the file does not completely erase it. When one does this, the computer just makes the file invisible to the user and marks the part of the disk that the file was stored on as "available”—meaning that your operating system can now write over the file with new data. Therefore, it may be weeks, months, or even years before that file is overwritten with a new one. Until this happens, that “deleted” file is still on your disk; it’s just invisible to normal operations. And with a little work and the right tools (such as “undelete” software or forensic methods), you can even still retrieve the “deleted” file. The bottom line is that computers normally don't "delete" files; they just allow the space those files take up to be overwritten by something else some time in the future.

    The best way to delete a file forever, then, is to make sure it gets overwritten immediately, in a way that makes it difficult to retrieve what used to be written there. Your operating system probably already has software that can do this for you—software that can overwrite all of the "empty" space on your disk with gibberish and thereby protect the confidentiality of deleted data.

    Note that securely deleting data from solid state drives (SSDs), USB flash drives, and SD cards is very hard! The instructions below apply only to traditional disk drives, and not to SSDs, which are becoming standard in modern laptops, USB keys/USB thumb drives, or SD cards/flash memory cards.

    This is because these types or drives use a technique called wear leveling. (You can read more about why this causes problems for secure deletion here.)

    If you’re using an SSD or a USB flash drive, you can jump to the section below.

    Secure Deletion on Mac OS X Anchor link

    On OS X 10.4 to 10.10, you can securely delete files by moving them to the Trash and then selecting Finder > Secure Empty Trash.

    The Secure Empty Trash feature was removed in OS X 10.11, because Apple felt that it could not guarantee secure deletion on the fast flash (SSD) drives that most of its modern models now use.

    If you use a traditional hard drive, and are comfortable with the command line, you can still use the Mac's srm command to overwrite the file. Fuller instructions (in English) are available here.

    A Warning About the Limitations of Secure Deletion Tools Anchor link

    First, remember that the advice above only deletes files on the disk of the computer you’re using. None of the tools above will delete backups that were made to somewhere else on your computer, another disk or USB drive, a “Time Machine,” on an email server, or in the cloud. In order to securely delete a file, you must delete every copy of that file, everywhere it was stored or sent. Additionally, once a file is stored in the cloud (e.g. via Dropbox or some other file-sharing service) then there’s usually no way to guarantee that it will be deleted forever.

    Unfortunately, there’s also another limitation to secure deletion tools. Even if you follow the advice above and you’ve deleted all copies of a file, there is a chance that certain traces of deleted files may persist on your computer, not because the files themselves haven't been properly deleted, but because some part of the operating system or some other program keeps a deliberate record of them.

    There are many ways in which this could occur, but two examples should suffice to convey the possibility. On Windows or Mac OS, a copy of Microsoft Office may retain a reference to the name of a file in the "Recent Documents" menu, even if the file has been deleted (Office might sometimes even keep temporary files containing the contents of the file). On a Linux or other *nix system, OpenOffice may keep as many records as Microsoft Office, and a user's shell history file may contain commands that include the file's name, even though the file has been securely deleted. In practice, there may be dozens of programs that behave like this.

    It's hard to know how to respond to this problem. It is safe to assume that even if a file has been securely deleted, its name will probably continue to exist for some time on your computer. Overwriting the entire disk is the only way to be 100% sure the name is gone. Some of you may be wondering, "Could I search the raw data on the disk to see if there are any copies of the data anywhere?" The answer is yes and no. Searching the disk (e.g. by using a command like grep -ab /dev/ on Linux) will tell you if the data is present in plaintext, but it won't tell you if some program has compressed or otherwise coded references to it. Also be careful that the search itself does not leave a record! The probability that the file's contents may persist is lower, but not impossible. Overwriting the entire disk and installing a fresh operating system is the only way to be 100% certain that records of a file have been erased.

    Secure Deletion When Discarding Old Hardware Anchor link

    If you want to finally throw a piece of hardware away or sell it on eBay, you'll want to make sure no one can retrieve your data from it. Studies have repeatedly found that computer owners usually fail to do this―hard drives are often resold chock-full of highly sensitive information. So, before selling or recycling a computer, be sure to overwrite its storage media with gibberish first. And even if you're not getting rid of it right away, if you have a computer that has reached the end of its life and is no longer in use, it's also safer to wipe the hard drive before stashing the machine in a corner or a closet. Darik's Boot and Nuke is a tool designed for this purpose, and there are a variety of tutorials on how to use it across the web (including here).

    Some full-disk encryption software has the ability to destroy the master key, rendering a hard drive's encrypted contents permanently incomprehensible. Since the key is a tiny amount of data and can be destroyed almost instantaneously, this represents a much faster alternative to overwriting with software like Darik's Boot and Nuke, which can be quite time-consuming for larger drives. However, this option is only feasible if the hard drive was always encrypted. If you weren't using full-disk encryption ahead of time, you'll need to overwrite the whole drive before getting rid of it.

    Discarding CD-ROMS Anchor link

    When it comes to CD-ROMs, you should do the same thing you do with paper―shred them. There are inexpensive shredders that will chew up CD-ROMs. Never just toss a CD-ROM out in the garbage unless you're absolutely sure there's nothing sensitive on it.

    Secure Deletion on Solid-state Disks (SSDs), USB Flash Drives, and SD Cards Anchor link

    Unfortunately due to the way SSDs, USB flash drives, and SD cards work, it is difficult, if not impossible, to securely delete both individual files and free space. As a result your best bet in terms of protection is to use encryption—that way, even if the file is still on the disk, it will at least look like gibberish to anyone who gets ahold of it and can’t force you to decrypt it. At this point in time, we cannot provide a good general procedure that will definitely remove your data from an SSD. If you want to know why it’s so hard to delete data, read on.

    As we mentioned above, SSDs and USB flash drives use a technique called wear leveling. At a high level, wear leveling works as follows. The space on every disk is divided into blocks, kind of like the pages in a book. When a file is written to disk, it’s assigned to a certain block or set of blocks (pages). If you wanted to overwrite the file then all you would have to do is tell the disk to overwrite those blocks. But in SSDs and USB drives, erasing and re-writing the same block can wear it out. Each block can only be erased and rewritten a limited number of times before that block just won’t work anymore (the same way if you keep writing and erasing with a pencil and paper, eventually the paper might rip and be useless). To counteract this, SSDs and USB drives will try to make sure that the amount of times each block has been erased and rewritten is about the same, so that the drive will last as long as possible (thus the term wear leveling). As a side effect, sometimes instead of erasing and writing the block a file was originally stored on, the drive will instead leave that block alone, mark it as invalid, and just write the modified file to a different block. This is kind of like leaving the page in the book unchanged, writing the modified file on a different page, and then just updating the book’s table of contents to point to the new page. All of this occurs at a very low level in the electronics of the disk, so the operating system doesn’t even realize it’s happened. This means, however, that even if you try to overwrite a file, there’s no guarantee the drive will actually overwrite it—and that’s why secure deletion with SSDs is so much harder.

    Last reviewed: 
    2016-09-08
  • How to: Delete Your Data Securely on Windows

    Most of us think that a file on our computer is deleted once we put the file in our computer's trash folder and empty the trash; in reality, deleting the file does not completely erase it. When one does this, the computer just makes the file invisible to the user and marks the part of the disk that the file was stored on as "available”—meaning that your operating system can now write over the file with new data. Therefore, it may be weeks, months, or even years before that file is overwritten with a new one. Until this happens, that “deleted” file is still on your disk; it’s just invisible to normal operations. And with a little work and the right tools (such as “undelete” software or forensic methods), you can even still retrieve the “deleted” file. The bottom line is that computers normally don't "delete" files; they just allow the space those files take up to be overwritten by something else some time in the future.

    The best way to delete a file forever, then, is to make sure it gets overwritten immediately, in a way that makes it difficult to retrieve what used to be written there. Your operating system probably already has software that can do this for you—software that can overwrite all of the "empty" space on your disk with gibberish and thereby protect the confidentiality of deleted data.

    Note that securely deleting data from solid state drives (SSDs), USB flash drives, and SD cards is very hard! The instructions below apply only to traditional disk drives, and not to SSDs, which are becoming standard in modern laptops, USB keys/USB thumb drives, or SD cards/flash memory cards.

    This is because these types or drives use a technique called wear leveling. (You can read more about why this causes problems for secure deletion here.)

    If you’re using an SSD or a USB flash drive, you can jump to the section below.

    On Windows, we currently suggest using BleachBit. BleachBit is a free/open source secure deletion tool for Windows and Linux, and is much more sophisticated than the built-in Cipher.exe.

    BleachBit can be used to quickly and easily target individual files for secure deletion, or to implement periodic secure deletion policies. It is also possible to write custom file deletion instructions. Please check the documentation for further information.

    Getting BleachBit Anchor link

    You can get BleachBig on Windows by downloading the installer from the BleachBit download page

    Click on the BleachBit installer .exe link. You'll be taken to the download page.

    Many browsers will ask you to confirm whether you want to download this file. Internet Explorer 11 shows a bar at the bottom of the browser window with an orange border.

    For any browser it is best to first save the file before proceeding, so click the “Save” button. By default, most browsers save downloaded files in the Downloads folder.

    Installing BleachBit Anchor link

    Keep the Windows Explorer window open and double-click on BleachBit-1.6-setup. You'll be asked if you want to allow the installation of this program. Click the “Yes” button.

    A window will open asking you to select an installation language. Select the language you want and click the OK button.

    The next window will show you the GNU General Public License. Check the box acceptance box and click the Next button.

    In the next window BleachBit shows some customization options. You may leave the options as they are. We recommend removing the check mark from the Desktop option. Click the Next button.

    Now BleachBit will ask you to confirm whether you want to install again. Click the Install button.

    Finally, the BleachBit installer shows a window telling you the installation is complete. Click the Next button.

    The last window in the installer asks whether you want to run BleachBit. Remove the checkmark from the Run BleachBit option. Click the Finish button.

    Using BleachBit Anchor link

    BleachBit interface

    Go to the Start menu, click the Windows icon, and select BleachBit from the menu.

    A small window will open and confirm you want to open BleachBit.

    The main BleachBit window will open. BleachBit will detect several commonly installed programs and show special options for each program. BleachBit comes with four default settings.

    Using Presets

    BleachBit can wipe the traces Internet Explorer leaves behind using the Internet Explorer preset (however BleachBit cannot wipe traces from any other browser). Check the box next to Internet Explorer. Notice how all the boxes belonging the Cookies, Form history, History, and Temporary files option are also checked. You can uncheck them as needed. Click the Clean button.

    BleachBit will now clean up certain files and show you the progress.

    Securely Delete a Folder

    Click the File menu and select Shred Folders.

    A small window will open up. Select the folder you want to shred.

    BleachBit will ask you to confirm whether you want to permanently delete the files you selected. Click the Delete button.

    BleachBit will now show you the files you deleted. Notice that BleachBit securely deletes each file in the folder, then securely deletes the folder.

    Securely Delete a File

    Click the File menu and select Shred Files.

    A file selection window will open up. Select the files you want to shred.

    BleachBit will ask you to confirm whether you want to permanently delete the files you selected. Click the Delete button.

    BleachBit has a number of other features. The most useful may be to “wipe free space.” This will attempt to remove any traces of files you have already deleted. Often Windows will leave all or part of the data from deleted files in the remaining free space left on the hard drive.  “Wipe free space” will overwrite these supposedly empty parts of the hard drive with random data. Wiping free space can take a lot of time, depending on how much spare capacity your drive has.

    A Warning About the Limitations of Secure Deletion Tools Anchor link

    First, remember that the advice above only deletes files on the disk of the computer you’re using. None of the tools above will delete backups that were made to somewhere else on your computer, another disk or USB drive, a “Time Machine,” on an email server, or in the cloud. In order to securely delete a file, you must delete every copy of that file, everywhere it was stored or sent. Additionally, once a file is stored in the cloud (e.g. via Dropbox or some other file-sharing service) then there’s usually no way to guarantee that it will be deleted forever.

    Unfortunately, there’s also another limitation to secure deletion tools. Even if you follow the advice above and you’ve deleted all copies of a file, there is a chance that certain traces of deleted files may persist on your computer, not because the files themselves haven't been properly deleted, but because some part of the operating system or some other program keeps a deliberate record of them.

    There are many ways in which this could occur, but two examples should suffice to convey the possibility. On Windows or Mac OS, a copy of Microsoft Office may retain a reference to the name of a file in the "Recent Documents" menu, even if the file has been deleted (Office might sometimes even keep temporary files containing the contents of the file). On a Linux or other *nix system, OpenOffice may keep as many records as Microsoft Office, and a user's shell history file may contain commands that include the file's name, even though the file has been securely deleted. In practice, there may be dozens of programs that behave like this.

    It's hard to know how to respond to this problem. It is safe to assume that even if a file has been securely deleted, its name will probably continue to exist for some time on your computer. Overwriting the entire disk is the only way to be 100% sure the name is gone. Some of you may be wondering, "Could I search the raw data on the disk to see if there are any copies of the data anywhere?" The answer is yes and no. Searching the disk (e.g. by using a command like grep -ab /dev/ on Linux) will tell you if the data is present in plaintext, but it won't tell you if some program has compressed or otherwise coded references to it. Also be careful that the search itself does not leave a record! The probability that the file's contents may persist is lower, but not impossible. Overwriting the entire disk and installing a fresh operating system is the only way to be 100% certain that records of a file have been erased.

    Secure Deletion When Discarding Old Hardware Anchor link

    If you want to finally throw a piece of hardware away or sell it on eBay, you'll want to make sure no one can retrieve your data from it. Studies have repeatedly found that computer owners usually fail to do this―hard drives are often resold chock-full of highly sensitive information. So, before selling or recycling a computer, be sure to overwrite its storage media with gibberish first. And even if you're not getting rid of it right away, if you have a computer that has reached the end of its life and is no longer in use, it's also safer to wipe the hard drive before stashing the machine in a corner or a closet. Darik's Boot and Nuke is a tool designed for this purpose, and there are a variety of tutorials on how to use it across the web (including here).

    Some full-disk encryption software has the ability to destroy the master key, rendering a hard drive's encrypted contents permanently incomprehensible. Since the key is a tiny amount of data and can be destroyed almost instantaneously, this represents a much faster alternative to overwriting with software like Darik's Boot and Nuke, which can be quite time-consuming for larger drives. However, this option is only feasible if the hard drive was always encrypted. If you weren't using full-disk encryption ahead of time, you'll need to overwrite the whole drive before getting rid of it.

    Discarding CD-ROMS Anchor link

    When it comes to CD-ROMs, you should do the same thing you do with paper―shred them. There are inexpensive shredders that will chew up CD-ROMs. Never just toss a CD-ROM out in the garbage unless you're absolutely sure there's nothing sensitive on it.

    Secure Deletion on Solid-State Disks (SSDs), USB Flash Drives, and SD Cards Anchor link

    Unfortunately due to the way SSDs, USB flash drives, and SD cards work, it is difficult, if not impossible, to securely delete both individual files and free space. As a result your best bet in terms of protection is to use encryption—that way, even if the file is still on the disk, it will at least look like gibberish to anyone who gets ahold of it and can’t force you to decrypt it. At this point in time, we cannot provide a good general procedure that will definitely remove your data from an SSD. If you want to know why it’s so hard to delete data, read on.

    As we mentioned above, SSDs and USB flash drives use a technique called wear leveling. At a high level, wear leveling works as follows. The space on every disk is divided into blocks, kind of like the pages in a book. When a file is written to disk, it’s assigned to a certain block or set of blocks (pages). If you wanted to overwrite the file then all you would have to do is tell the disk to overwrite those blocks. But in SSDs and USB drives, erasing and re-writing the same block can wear it out. Each block can only be erased and rewritten a limited number of times before that block just won’t work anymore (the same way if you keep writing and erasing with a pencil and paper, eventually the paper might rip and be useless). To counteract this, SSDs and USB drives will try to make sure that the amount of times each block has been erased and rewritten is about the same, so that the drive will last as long as possible (thus the term wear leveling). As a side effect, sometimes instead of erasing and writing the block a file was originally stored on, the drive will instead leave that block alone, mark it as invalid, and just write the modified file to a different block. This is kind of like leaving the page in the book unchanged, writing the modified file on a different page, and then just updating the book’s table of contents to point to the new page. All of this occurs at a very low level in the electronics of the disk, so the operating system doesn’t even realize it’s happened. This means, however, that even if you try to overwrite a file, there’s no guarantee the drive will actually overwrite it—and that’s why secure deletion with SSDs is so much harder.

     

    Last reviewed: 
    2015-03-04
  • How to: Delete your Data Securely on Linux

    Most of us think that a file on our computer is deleted once we put the file in our computer's trash folder and empty the trash; in reality, deleting the file does not completely erase it. When one does this, the computer just makes the file invisible to the user and marks the part of the disk that the file was stored on as "available”—meaning that your operating system can now write over the file with new data. Therefore, it may be weeks, months, or even years before that file is overwritten with a new one. Until this happens, that “deleted” file is still on your disk; it’s just invisible to normal operations. And with a little work and the right tools (such as “undelete” software or forensic methods), you can even still retrieve the “deleted” file. The bottom line is that computers normally don't "delete" files; they just allow the space those files take up to be overwritten by something else some time in the future.

    The best way to delete a file forever, then, is to make sure it gets overwritten immediately, in a way that makes it difficult to retrieve what used to be written there. Your operating system probably already has software that can do this for you—software that can overwrite all of the "empty" space on your disk with gibberish and thereby protect the confidentiality of deleted data.

    Note that securely deleting data from solid state drives (SSDs), USB flash drives, and SD cards is very hard! The instructions below apply only to traditional disk drives, and not to SSDs, which are becoming standard in modern laptops, USB keys/USB thumb drives, or SD cards/flash memory cards.

    This is because these types or drives use a technique called wear leveling. (You can read more about why this causes problems for secure deletion here.)

    If you’re using an SSD or a USB flash drive, you can jump to the section below.

    On Linux, we currently suggest using BleachBit. BleachBit is a free/open source secure deletion tool for Windows and Linux, and is much more sophisticated than the built-in “shred.”

    BleachBit can be used to quickly and easily target individual files for secure deletion, or to implement periodic secure deletion policies. It is also possible to write custom file deletion instructions. Please check the documentation for further information.

    Installing BleachBit Anchor link

    Installing with the Ubuntu Software Center

    You can get BleachBit on Ubuntu Linux by using the Ubuntu Software Center. Click on the Application button in the upper left menu and use the search field.

    Type “software” in the search field and click the Ubuntu Software icon.

    You can browse through the Ubuntu Software Center to look for BleachBit but searching is faster. Use the search field.

    Enter “bleachbit” in the search field and press enter and BleachBit will display as a result.

    Click on BleachBit and click the Install button.

    The Ubuntu Software Center will ask for your password for permission. Enter your password and click the Authenticate button.

    The Ubuntu Software Center will install BleachBit and show you a small progress bar. When the installation is done you will see a Remove button.

    Installing From the Terminal Anchor link

    You can get BleachBit on Ubuntu Linux by using the Terminal. Click on the Application button in the upper left menu and use the search field. 

    Type “sudo apt-get install bleachbit” and press the Enter.

    You are asked to enter your password to verify that you want to install BleachBit. Enter your password and press Enter.

    Now you'll see the progress of the installation of BleachBit and when it is done you should be back at the command line where you started.

    Adding BleachBit to sidebar Anchor link

    Click on the Application button in the upper left menu and use the search field.

    Type “bleach” in the search field and two options will appear: BleachBit and BleachBit (as root). The BleachBit (as root) option should only be used if you know what you are doing and can cause irreparable harm if you use it to delete files needed by the operating system.

    Right-click on BleachBit and select “Add to Favorites.”

    Using BleachBit Anchor link

    Click on the Application button in the upper left menu and click on BleachBit from the favorites.

    The main BleachBit window will open.

    First BleachBit gives us an overview of the preferences. We recommend checking the “Overwrite files to hide contents” option.

    Click the Close button.

    BleachBit will detect several commonly installed programs and will show special option for each program. BleachBit comes with four default settings.

    Using Presets

    Some software leaves behind records of when and how it was used. Two important examples that merely begin to illustrate this widespread issue are Recent Documents and web browser history. Software that tracks the recently-edited documents leaves a record of the names of files you've been working with, even if those files themselves have been deleted. And web browsers usually keep detailed records of what sites you've visited recently, and even keep cached copies of pages and images from those sites to make them load faster next time you visit.

    Bleachbit provides "presets" that can remove some of these records for you, based on the Bleachbit authors' research about locations of records on your computer that tend to reveal your previous activity. We'll describe using just two of these presets so you can get an idea of how they work.

    Check the box next to System. Notice that this marks all the checkboxes under the System category. Uncheck the System box and check the following boxes: Recent document list and Trash. Click the Clean button.

    BleachBit will now ask you for confirmation. Click the Delete button.

    BleachBit will now clean up certain files and show you the progress.

    Securely Delete a Folder

    Click the File menu and select Shred Folders.

    A small window will open up. Select the folder you want to shred.

    BleachBit will ask you to confirm whether you want to permanently delete the files you selected. Click the Delete button.

    BleachBit will now show you the files you deleted. Notice that BleachBit securely deletes each file in the folder, then securely deletes the folder.

    Securely Delete a File

    Click the File menu and select Shred Files.

    A file selection window will open up. Select the files you want to shred.

    BleachBit will ask you to confirm whether you want to permanently delete the files you selected. Click the Delete button.

    A Warning About the Limitations of Secure Deletion Tools Anchor link

    First, remember that the advice above only deletes files on the disk of the computer you’re using. None of the tools above will delete backups that were made to somewhere else on your computer, another disk or USB drive, a “Time Machine,” on an email server, or in the cloud. In order to securely delete a file, you must delete every copy of that file, everywhere it was stored or sent. Additionally, once a file is stored in the cloud (e.g. via Dropbox or some other file-sharing service) then there’s usually no way to guarantee that it will be deleted forever.

    Unfortunately, there’s also another limitation to secure deletion tools. Even if you follow the advice above and you’ve deleted all copies of a file, there is a chance that certain traces of deleted files may persist on your computer, not because the files themselves haven't been properly deleted, but because some part of the operating system or some other program keeps a deliberate record of them.

    There are many ways in which this could occur, but two examples should suffice to convey the possibility. On Windows or Mac OS, a copy of Microsoft Office may retain a reference to the name of a file in the "Recent Documents" menu, even if the file has been deleted (Office might sometimes even keep temporary files containing the contents of the file). On a Linux or other *nix system, OpenOffice may keep as many records as Microsoft Office, and a user's shell history file may contain commands that include the file's name, even though the file has been securely deleted. In practice, there may be dozens of programs that behave like this.

    It's hard to know how to respond to this problem. It is safe to assume that even if a file has been securely deleted, its name will probably continue to exist for some time on your computer. Overwriting the entire disk is the only way to be 100% sure the name is gone. Some of you may be wondering, "Could I search the raw data on the disk to see if there are any copies of the data anywhere?" The answer is yes and no. Searching the disk (e.g. by using a command like grep -ab /dev/ on Linux) will tell you if the data is present in plaintext, but it won't tell you if some program has compressed or otherwise coded references to it. Also be careful that the search itself does not leave a record! The probability that the file's contents may persist is lower, but not impossible. Overwriting the entire disk and installing a fresh operating system is the only way to be 100% certain that records of a file have been erased.

    Secure Deletion When Discarding Old Hardware Anchor link

    If you want to finally throw a piece of hardware away or sell it on eBay, you'll want to make sure no one can retrieve your data from it. Studies have repeatedly found that computer owners usually fail to do this―hard drives are often resold chock-full of highly sensitive information. So, before selling or recycling a computer, be sure to overwrite its storage media with gibberish first. And even if you're not getting rid of it right away, if you have a computer that has reached the end of its life and is no longer in use, it's also safer to wipe the hard drive before stashing the machine in a corner or a closet. Darik's Boot and Nuke is a tool designed for this purpose, and there are a variety of tutorials on how to use it across the web (including here).

    Some full-disk encryption software has the ability to destroy the master key, rendering a hard drive's encrypted contents permanently incomprehensible. Since the key is a tiny amount of data and can be destroyed almost instantaneously, this represents a much faster alternative to overwriting with software like Darik's Boot and Nuke, which can be quite time-consuming for larger drives. However, this option is only feasible if the hard drive was always encrypted. If you weren't using full-disk encryption ahead of time, you'll need to overwrite the whole drive before getting rid of it.

    Discarding CD-ROMS Anchor link

    When it comes to CD-ROMs, you should do the same thing you do with paper―shred them. There are inexpensive shredders that will chew up CD-ROMs. Never just toss a CD-ROM out in the garbage unless you're absolutely sure there's nothing sensitive on it.

    Secure Deletion on Solid-state Disks (SSDs), USB Flash Drives, and SD Cards Anchor link

    Unfortunately due to the way SSDs, USB flash drives, and SD cards work, it is difficult, if not impossible, to securely delete both individual files and free space. As a result your best bet in terms of protection is to use encryption—that way, even if the file is still on the disk, it will at least look like gibberish to anyone who gets ahold of it and can’t force you to decrypt it. At this point in time, we cannot provide a good general procedure that will definitely remove your data from an SSD. If you want to know why it’s so hard to delete data, read on.

    As we mentioned above, SSDs and USB flash drives use a technique called wear leveling. At a high level, wear leveling works as follows. The space on every disk is divided into blocks, kind of like the pages in a book. When a file is written to disk, it’s assigned to a certain block or set of blocks (pages). If you wanted to overwrite the file then all you would have to do is tell the disk to overwrite those blocks. But in SSDs and USB drives, erasing and re-writing the same block can wear it out. Each block can only be erased and rewritten a limited number of times before that block just won’t work anymore (the same way if you keep writing and erasing with a pencil and paper, eventually the paper might rip and be useless). To counteract this, SSDs and USB drives will try to make sure that the amount of times each block has been erased and rewritten is about the same, so that the drive will last as long as possible (thus the term wear leveling). As a side effect, sometimes instead of erasing and writing the block a file was originally stored on, the drive will instead leave that block alone, mark it as invalid, and just write the modified file to a different block. This is kind of like leaving the page in the book unchanged, writing the modified file on a different page, and then just updating the book’s table of contents to point to the new page. All of this occurs at a very low level in the electronics of the disk, so the operating system doesn’t even realize it’s happened. This means, however, that even if you try to overwrite a file, there’s no guarantee the drive will actually overwrite it—and that’s why secure deletion with SSDs is so much harder.

    Last reviewed: 
    2015-03-06
  • Keeping Your Data Safe

    One of the greatest challenges of defending your data from those who might want it is the sheer size of the information you store or carry, and the ease by which it can be taken from you. Many of us carry entire histories of our contacts, our communications, and our current documents on laptops, or even mobile phones. That data can include confidential information of dozens, even thousands, of people. A phone or laptop can be stolen, or copied in seconds.

    The United States is just one of many countries that seizes and copies data at borders. Data can be taken from you at roadblocks, grabbed from you in the street, or burgled from your house.

    Just as you can keep your communications safer with encryption, you can also make it harder for those who physically steal data to unlock its secrets. Computers and mobile phones can be locked by passwords, PINs or gestures, but these locks do not help protect data if the device itself is seized. It's relatively simple to bypass these locks, because your data is stored in an easily readable form within the device. All an attacker needs to do is to access the storage directly, and the data can be copied or examined without knowing your password.

    If you use encryption, your adversary needs not just your device, but also your password to unscramble the encrypted data—there's no shortcut.

    It's safest and easiest to encrypt all of your data, not just a few folders. Most computers and smartphones offer complete, full-disk encryption as an option. Android offers it under its "Security" settings, Apple devices such as the iPhone and iPad describe it as "Data Protection" and turn it on if you set a passcode. On computer running Windows Pro, it's known as "BitLocker." 

    BitLocker's code is closed and proprietary, which means it is hard for external reviewers to know exactly how secure it is. Using BitLocker requires you trust Microsoft provides a secure storage system without hidden vulnerabilities. On the other hand, if you're already using Windows, you are already trusting Microsoft to the same extent. If you are worried about surveillance from the kind of attackers who might know of or benefit from a back door in either Windows or BitLocker, you may wish to consider an alternative open source operating system such as GNU/Linux or BSD, especially a version that has been hardened against security attacks, such Tails or Qubes OS.

    Apple provides a built-in full disk encryption feature on macOS called FileVault.  On Linux distributions, full-disk encryption is usually offered when you first set up your system. At the time this guide was updated, we do not have a full disk encryption tool for versions of Windows that do not include BitLocker that we can recommend.

    Whatever your device calls it, encryption is only as good as your password. If your attacker has your device, they have all the time in the world to try out new passwords. Forensic software can try millions of passwords a second. That means that a four number pin is unlikely to protect your data for very long at all, and even a long password may merely slow down your attacker. A really strong password under these conditions should be over fifteen characters long.

    Most of us are not realistically going to learn and enter such passphrases on our phones or mobile devices. So while encryption can be useful to prevent casual access, you should preserve truly confidential data by keeping it hidden from physical access by attackers, or cordoned away on a much more secure machine.

    Create a Secure Machine Anchor link

    Maintaining a secure environment can be hard work. At best, you have to change passwords, habits, and perhaps the software you use on your main computer or device. At worst, you have to constantly think about whether you're leaking confidential information or using unsafe practices. Even when you know the problems, some solutions may be out of your hands. Other people might require you to continue unsafe digital security practices even after you have explained the dangers. For instance, work colleagues might want you to continue to open email attachments from them, even though you know your attackers could impersonate them and send you malware. Or you may be concerned that your main computer has already been compromised.

    One strategy to consider is cordoning off valuable data and communications onto a more secure computer. Use that machine only occasionally, and when you do, consciously take much more care over your actions. If you need to open attachments, or use insecure software, do it on another machine.

    If you're setting up a secure machine, what extra steps can you take to make it secure?

    You can almost certainly keep the device in a more physically safe place: somewhere where you are able to tell if it has been tampered with, such as a locked cabinet.

    You can install a privacy- and security-focused operating system like Tails. You might not be able (or want) to use an open source operating system in your everyday work, but if you just need to store, edit and write confidential emails or instant messages from this secure device, Tails will work well, and defaults to high security settings.

    An extra, secure computer may not be as expensive an option as you think. A computer that is seldom used, and only runs a few programs, does not need to be particularly fast or new. You can buy an older netbook for a fraction of the price of a modern laptop or phone. Older machines also have the advantage that secure software like Tails may be more likely to work with them than newer models.

    You can use the secure machine to keep the primary copy of confidential data. A secure machine can be valuable in cordoning off private data in this way, but you should also consider a couple of extra risks it might create. If you concentrate your most treasured information onto this one computer, it may make it more of an obvious target. Keep it well hidden, don't discuss its location, and don't neglect to encrypt the computer's drive with a strong password, so that if it is stolen, the data will remain unreadable without the password safe.

    Another risk is the danger that destroying this one machine will destroy your only copy of the data.

    If your adversary would benefit from you losing all your data, don't keep it in just one place, no matter how secure. Encrypt a copy and keep it somewhere else.

    The highest level of protection from Internet attacks or online surveillance is, not surprisingly, not connecting to the Internet at all. You could make sure your secure computer never connects to a local network or Wifi, and only copy files onto the machine using physical media, like DVDs or USB drives. In network security, this is known as having an "air gap" between the computer and the rest of the world. Not many people go this far, but it can be an option if you want to keep data that is rarely accessed but you never want to lose. Examples might be an encryption key you only use for important messages (like "My other encryption keys are now insecure"), a list of passwords or instructions for other people to find if you are unavailable, or a backup copy of someone else's private data that has been entrusted to you. In most of these cases, you might want to consider just having a hidden storage device, rather than a full computer. An encrypted USB key kept safely hidden is probably as useful (or as useless) as a complete computer unplugged from the Internet.

    If you do use the secure device to connect to the Internet, you might choose not to log in or use your usual accounts. Create separate web or email accounts that you use for communications from this device, and use Tor to keep your IP address hidden from those services. If someone is choosing to specifically target your identity with malware, or is only intercepting your communications, separate accounts and Tor can help break the link between your identity, and this particular machine.

    A variation on the idea of a secure machine is to have an insecure machine: a device that you only use when you are going into dangerous places or need to try a risky operation. Many journalists and activists, for instance, take a minimal netbook with them when they travel. This computer does not have any of their documents, usual contact or email information on it, and so is less of a loss if it is confiscated or scanned. You can apply the same strategy to mobile phones. If you usually use a smartphone, consider buying a cheap throwaway or burner phone when travelling or for specific communications.

    Last reviewed: 
    2016-12-01
  • Protecting Yourself on Social Networks

    Social networking sites are some of the most popular websites and tools we use on the Internet. Facebook, Google+, and Twitter have hundreds of millions of users each.

    Social networks are often built on the idea of sharing posts, photographs, and personal information. Yet they have also become forums for organizing and speech—much of which relies on privacy and pseudonymity. Thus, the following questions are important to consider when using social networks: How can I interact with these sites while protecting myself? My basic privacy? My identity? My contacts and associations? What information do I want keep private and who do I want to keep it private from?

    Depending on your circumstances, you may need to protect yourself against the social media site itself, against other users of the site, or both.

    Here are some tips to keep in mind when you’re setting up your account:

    Registering for a Social Media Site Anchor link

    • Do you want to use your real name? Some social media sites have so-called "real name policies," but these have become more lax over time. If you do not want to use your real name when registering for a social media site, do not.
    • When you register, don't provide more information than is necessary. If you are concerned with hiding your identity, use a separate email address. Be aware that your IP address may be logged at registration.
    • Choose a strong password and, if possible, enable two-factor authentication.
    • Beware of password recovery questions whose answers can be mined from your social media details. For example: “What city were you born in?” or “What is the name of your pet?” You may want to choose password recovery answers that are false. One good way to remember the answers to password recovery questions, should you choose to use false answers for added security, is to note your chosen answers in a password safe.

    Check the Social Media Site's Privacy Policy Anchor link

    Remember that information stored by third parties is subject to their own policies and may be used for commercial purposes or shared with other companies, for example, marketing firms. We know that reading privacy policies is a near-impossible task, but you may want to take a look at sections on how your data is used, when it is shared with other parties, and how the service responds to law enforcement requests.

    Social networking sites, usually for-profit businesses, often collect sensitive information beyond what you explicitly input—where you are, what interests and advertisements you react to, what other sites you've visited (e.g. through "Like" buttons). It can be helpful to block third-party cookies and use tracker-blocking browser extensions to make sure extraneous information isn't being passively transmitted to third parties.

    Some social networking sites, like Facebook and Twitter, have business relationships with data brokers in order to target advertisements more effectively. EFF has guides that walk you through how to opt-out of these tracking schemes:

    Change Your Privacy Settings Anchor link

    Specifically, change the default settings. For example, do you want to share your posts with the public, or only with a specific group of people? Should people be able to find you using your email address or phone number? Do you want your location shared automatically?

    Remember, privacy settings are subject to change. Sometimes, these privacy settings get stronger and more granular; sometimes not. Be sure to pay attention to these changes closely to see if any information that was once private will be shared, or if any additional settings will allow you to take more control of your privacy.

    Your Social Graph Anchor link

    Remember that you’re not the only person who can give away potentially sensitive data about yourself. Your friends can tag you in photos, report your location, and make their connections to you public in a variety of ways. You may have the option of untagging yourself from these posts, but privacy does not work retroactively. You may want to talk to your friends about what you do and do not feel comfortable having them share about you in public.

    Last reviewed: 
    2015-02-10
  • How to: Circumvent Online Censorship

    This is a short overview to circumventing online censorship, but is by no means comprehensive. For a more in-depth guide on how to circumvent online censorship, check out FLOSS Manuals’ guide, Bypassing Censorship.

    Many governments, companies, schools, and public access points use software to prevent Internet users from accessing certain websites and Internet services. This is called Internet filtering or blocking and is a form of censorship. Content filtering comes in different forms. Sometimes entire websites are blocked, sometimes individual web pages, and sometimes content is blocked based on keywords contained in it. One country might block Facebook entirely, or only block particular Facebook group pages—or it might block any page or web search with the words “falun gong” in it.

    Regardless of how content is filtered or blocked, you can almost always get the information you need by using a circumvention tool. Circumvention tools usually work by diverting your web or other traffic through another computer, so that it bypasses the machines conducting the censorship. An intermediary service through which you channel your communications in this process is called a proxy.

    Circumvention tools do not necessarily provide additional security or anonymity, even those that promise privacy or security, even ones that have terms like “anonymizer” in their names.

    There are different ways of circumventing Internet censorship, some of which provide additional layers of security. The tool that is most appropriate for you depends on your threat model.

    If you’re not sure what your threat model is, start here.

    Basic Techniques Anchor link

    HTTPS is the secure version of the HTTP protocol used to access websites. Sometimes a censor will block the insecure version of a site only, allowing you to access that site simply by entering the version of the domain that starts with HTTPS. This is particularly useful if the filtering you're experiencing is based on keywords or only blocks individual web pages. HTTPS stops censors from reading your web traffic, so they cannot tell what keywords are being sent, or which individual web page you are visiting (censors can still see the domain names of all websites you visit).

    If you suspect this type of simple blocking, try entering https:// before the domain in place of http://.

    Try EFF’s HTTPS Everywhere plug-in to automatically turn on HTTPS for those sites that support it.

    Another way that you may be able to circumvent basic censorship techniques is by trying an alternate domain name or URL. For example, instead of visiting http://twitter.com, you might visit http://m.twitter.com, the mobile version of the site. Censors that block websites or web pages usually work from a blacklist of banned websites, so anything that is not on that blacklist will get through. They might not know of all the variations of a particular website's domain name—especially if the site knows it is blocked and registers more than one name.

    Web-based Proxies Anchor link

    A web-based proxy (such as http://proxy.org/) is a good way of circumventing censorship. In order to use a web-based proxy, all you need to do is enter the filtered address that you wish to use; the proxy will then display the requested content.

    Web-based proxies a good way to quickly access blocked websites, but often don’t provide any security and will be a poor choice if your threat model includes someone monitoring your internet connection. Additionally, they will not help you to use other blocked non-webpage services such as your instant messaging program. Finally, web-based proxies themselves pose a privacy risk for many users, depending on their threat model, since the proxy will have a complete record of everything you do online.

    Encrypted Proxies Anchor link

    There are numerous proxy tools that utilize encryption, providing an additional layer of security, as well as the ability to bypass filtering. Although the connection is encrypted, the tool provider may have your personal data, meaning that these tools do not provide anonymity. They are, however, more secure than a plain web-based proxy.

    The simplest form of an encrypted web proxy is one that starts with “https”—this will use the encryption usually provided by secure websites. Ironically, in the process, the owners of these proxies will get to see the data you send to and from other secure websites, so be cautious.

    Other tools use a hybrid approach—they act like a proxy, but contain elements of the encrypted services listed below. Examples of these tools include Ultrasurf and Psiphon.

    Virtual Private Networks Anchor link

    A Virtual Private Network (VPN) encrypts and sends all Internet data between your computer and another computer. This computer could belong to a commercial or nonprofit VPN service, your company, or a trusted contact. Once a VPN service is correctly configured, you can use it to access webpages, e-mail, instant messaging, VoIP and any other Internet service. A VPN protects your traffic from being intercepted locally, but your VPN provider can keep logs of your traffic (websites you access, and when you access them) or even provide a third party with the ability to snoop directly on your web browsing. Depending on your threat model, the possibility of a government listening in on your VPN connection or obtaining the logs may be a significant risk and, for some users, could outweigh the short-term benefits of using a VPN.

    For information about specific VPN services, click here. Disclaimer: some VPNs with exemplary privacy policies could well be run by devious people. Do not use a VPN that you do not trust.

    Tor Anchor link

    Tor is free and open-source software that is intended to provide you with anonymity, but which also allows you to circumvent censorship. When you use Tor, the information you transmit is safer because your traffic is bounced around a distributed network of servers, called relays. This could provide anonymity, since the computer with which you’re communicating will never see your IP address, but instead will see the IP address of the last Tor router through which your traffic traveled.

    When used with a couple of optional features (bridges and pluggable transports) Tor is the gold standard for secure censorship circumvention against a local state, since it will both bypass almost all national censorship, and if properly configured, protect your identity from an adversary listening in on your country’s networks. It can be slow and hard to use, however.

    To learn how to use Tor, click here

    Last reviewed: 
    2015-08-14
  • What Is Encryption?

    Encryption is the mathematical science of codes, ciphers, and secret messages. Throughout history, people have used encryption to send messages to each other that (hopefully) couldn't be read by anyone besides the intended recipient.

    Today, we have computers that are capable of performing encryption for us. Digital encryption technology has expanded beyond simple secret messages; today, encryption can be used for more elaborate purposes, for example to verify the author of messages or to browse the Web anonymously with Tor.

    Under some circumstances, encryption can be fairly automatic and simple. But there are ways encryption can go wrong, and the more you understand it, the safer you will be against such situations.

    Three Concepts to Understand in Encryption Anchor link

    Private and Public Keys

    One of the most important concepts to understand in encryption is a key. Common types of encryption include a private key, which is kept secret on your computer and lets you read messages that are intended only for you. A private key also lets you place unforgeable digital signatures on messages you send to other people. A public key is a file that you can give to others or publish that allows people to communicate with you in secret, and check signatures from you. Private and public keys come in matched pairs, like the halves of a rock that has been split into two perfectly matching pieces, but they are not the same.

    Security Certificates

    Another extremely valuable concept to understand is a security certificate. The Web browser on your computer can make encrypted connections to sites using HTTPS. When they do that, they examine certificates to check the public keys of domain names—(like www.google.com, www.amazon.com, or ssd.eff.org). Certificates are one way of trying to determine if you know the right public key for a person or website, so that you can communicate securely with them.

    From time to time, you will see certificate-related error messages on the Web. Most commonly, this is because a hotel or cafe network is trying to break your secret communications with the website. It is also common to see an error because of a bureaucratic mistake in the system of certificates. But occasionally, it is because a hacker, thief, police agency, or spy agency is breaking the encrypted connection.

    Unfortunately, it is extremely difficult to tell the difference between these cases. This means you should never click past a certificate warning if it relates to a site where you have an account, or are reading any sensitive information.

    Key Fingerprints

    The word "fingerprint" means lots of different things in the field of computer security. One use of the term is a "key fingerprint," a string of characters like "342e 2309 bd20 0912 ff10 6c63 2192 1928" that should allow you to uniquely and securely check that someone on the Internet is using the right private key. If you check that someone's key fingerprint is correct, that gives you a higher degree of certainty that it's really them. But it's not perfect, because if the keys are copied or stolen someone else would be able to use the same fingerprint.

    Last reviewed: 
    2015-04-22
JavaScript license information