Matching User Expectations

About two months ago, I mentioned that one Facebook application had a hole which allowed me to view the photo albums of any Facebook user whose privacy settings allowed it.  I imagine that many users do not realize that access for “Everybody” is the default setting when creating a new album, so while the issue did not technically violate anyone’s privacy, it would probably come as a surprise to many people.

Turns out developers had already built applications whose sole purpose was accessing public photo albums.  Since these albums were set to public access, the applications simply made API calls consistent with the album’s privacy settings.  CNET News now reports that Facebook has taken action to prevent such access via the API.  Since the albums are still public, you could still access them if you had the direct URI, but the difficulty of finding the URI gives users the illusion of control without requiring them to understand the ramifications of the default setting.

The key to this whole story can be found in this statement from the CNET article:

A Facebook spokesperson said the company made the change so the technology more closely matched users’ privacy expectations.

Some people seem to think that Facebook should be more public and open – that users should get over any illusions of keeping information private on the Internet and embrace free exchange of ideas without annoying filters and controls.  People endorsing this perspective may wonder why I spend so much time talking about privacy on Facebook.  For instance, some may view highly targeted advertising as a benefit, since it can provide users with relevant ads that link them to services they would want.

I recall a blogger (I can’t remember where I read this; if anyone has a link, please let me know so I can give credit where it’s due) once remarking that if a site uses someone’s personal information in an unexpected way, that’s an invasion of privacy, but if something useful happens in an expected way, it’s a feature.  Privacy comes back to user expectations.

And that’s one of the major problems I see with privacy on Facebook right now.  I don’t consider myself a “privacy fundamentalist.”  I simply believe users should have control over their information and be aware of how it’s used.  If Facebook users want public profiles or highly targeted advertising, so be it.  But make sure those users are aware of what’s going on – sell them on the benefits while being realistic about the risks.

If social networking sites want to strike a good balance on privacy, they need to match user expectations.  Adding new features may require changing those expectations (the News Feed comes to mind), and that can happen through education, other helpful features, and time.  But iwhen the state of privacy on a site races ahead of what users expect to happen, that’s a problem waiting to happen.

And that’s the way I see Facebook right now.  Vulnerabilities in applications leave personal information at risk.  Application advertising networks process vast quantities of personal information to target ads (yes, Facebook does too, but their relationship to the user is quite different).  Rogue applications can steal personal information.  All the while, Facebook trumpets their extensive privacy controls, and I continue to get shocked reactions when I explain or demonstrate to people what’s actually happening with their personal information.

And that’s why I keep talking about privacy in social networking applications.

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The Limits of Application Privacy Limits

One issue I have not discussed much previously is how much of your data an application can access via a friend’s session.  I and others have had to sort through some confusion on this topic, and I appreciate recent work by Ian Glazer to clear things up.  As you can see from my comments on Glazer’s second post about his Privacy Mirror, I did not fully understand how things worked until Glazer posted his more detailed explanation of his findings:

It shouldn’t take a few hundred lines of PHP, three debuggers, and an engineering degree to figure out how privacy controls work. This lack of clarity robs Facebook users of the opportunity to make meaningful and informed choices about their privacy.

What Glazer found is that when a user restricts how much profile data is available to applications through friend’s sessions, those restrictions only apply if the user does not also authorize the application.  Once you install an application, all of your data is available in any friend’s session (subject to profile restrictions).

In Facebook’s defense, they do technically say this on the application privacy settings page, though I think it could be made more clear.  I certainly didn’t comprehend all the ramifications at first:

When a friend of yours allows an application to access their information, that application may also access any information about you that your friend can already see….

You can use the controls on this page to limit what types of information your friends can see about you through applications. Please note that this is only for applications you do not use yourself…

One could easily argue that this is a case of incompetence on my part for not making sense of what Facebook said, but I know that other security researchers have also missed some of these caveats or didn’t put them all together.

As Glazer points out, Facebook provides an easy way to tell how much information a friend can access via your profile, but provides no simple way for letting you know how much data applications can access.  Apparently, though, the answer is rather simple, since besides a few special cases, an application still basically has full access.

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Debunking Facebook’s Statements on Ads

I never want to come across to harshly when talking about Facebook; I honestly believe they want to protect user privacy and security.  But while Facebook continues to hone and publicize the privacy controls in their own features, they seem to ignore major issues with Facebook applications.  Some might argue that applications are not under Facebook’s control, but this ignores changes Facebook could make which would help protect users.  I can only think that Facebook does not want to risk alienating developers any further.

In turn, many developers seem to shift responsibility to end users.  Recently I read back over coverage from ReadWriteWeb and the BBC on rogue Facebook applications, along with a discussion on Facebook’s developer forum.  While the reports admittedly included sensationalist elements, I was surprised to see commenters taking the position that rogue applications weren’t a problem, since users authorize applications to access their profile data.  In essence, if an application steals data, it’s the user’s fault for letting it.

This perspective fails to take into account the average user’s understanding of how applications access and share data, not to mention how little control a user has over applications.  And most users would probably be shocked by how even mainstream applications make use of profile information to target advertisements.  Many of these applications and advertising networks again take a hands-off approach, noting that a user could opt out of such programs.  But what are the chances of a user even realizing this, much less taking the time to figure out how?

Advertising in applications made a few headlines this weekend, after a message on user privacy made the rounds on Facebook.  The message did not actually address application ads, but in a statement on the message, Facebook deflected attention from their own ads to talk about application ads, and painted a rather rosy picture of user privacy on the Platform.  I respectfully disagree with their assessment.

First, let’s clarify: the original viral message on profile pictures in ads pointed to an actual privacy setting which controls whether your profile picture appears in Facebook Ads.  This was never about the application ad networks Facebook brought up in their statement.

Second, consider why Facebook banned SocialHour and SocialReach.  From what I understood at the time, Facebook had a problem with the ads falsely implying that friends had taken certain actions (e.g. taking a quiz).  Facebook did not seem to address the issue of profile pictures being used in the advertisements, and the practice has continued on many advertising networks to this day.

I was honestly rather surprised by Facebook’s statement, since it seemed to imply that all was well with application advertising.  I then became shocked when I read the update Nick O’Neill posted after digging for more information:

I’ve spoken to Facebook and they’ve made some relatively strong statements, the most important of which was that ad networks “need permission from the owner of whatever photo they use.” That means unless an ad network asked for permission to use your image, they can’t use it. Additionally, here are the policies that are applicable according to Facebook:

  • The data section of the platform guidelines indicates that just because a developer gets access to user data doesn’t mean that they can use it
  • Developers are not allowed to pass user data they get from FB to ad networks.
  • Apps cannot break the law, and there are rights of publicity issues that come into play here. Facebook is granted permission in the terms to use a user’s photo in an ad but this permission does not extend to developers or ad networks.
  • Not doing anything misleading (indicating a user has taken a quiz when they haven’t is misleading)

Seriously?  Seriously? It doesn’t take long to realize how flagrantly these guidelines are being ignored:

  1. Many application ad networks use the profile pictures of users and their friends.
  2. Application ad networks routinely access loads of profile data from users and their friends.  This information is often processed client-side and not sent back to the ad network servers, but you’d probably be stunned at just how much data is sifted through.
  3. User data is routinely sent back to application ad networks.  I can cite several examples of this, but I hadn’t brought them up sooner as I’ve been working on sorting through them and gathering records of what happens.  I did mention one example over a month ago on this very blog, yet the methods of that particular ad network have not changed at all in the mean time, nor has Facebook taken any action against them.
  4. The session secret of an application is routinely passed on to application ad networks.  This enables the ad network server to make requests to Facebook via the API and access user data.  Regardless of whether such action happens (and it does, by the way), an application should never share its session secret with outside web sites.  In several cases, the session secret is inadverently recorded by Google Analytics – and that includes ad network Analytics accounts.

As an example of ad networks accessing user data, remember SocialReach?  This very moment, one application with over 10 million monthly active users is serving SocialReach ads scripts which make Facebook API requests from the SocialReach web site.  These are the same FQL queries SocialReach made prior to Facebook banning it a while back. Update: On further investigation, it appears the SocialReach code operates client-side, though the session secret is still passed on to SocialReach and the code does make API requests.

As I said, I’ve been planning to talk more about this, but was still working on putting everything together and making further investigations.  With the sudden press about application advertising, I figured I should go ahead and at least note how badly reality differs from what Facebook seems to be trying to portray.  If news sites want proof or more specifics on the problems I’ve described, feel free to get in touch.

Part of what leaves me bewildered is that if I can uncover so many problems in my research, how does Facebook not notice them?  Some of these issues are even occurring in Facebook Verified Applications.  I simply don’t understand how Facebook can make the kinds of statements AllFacebook published in light of all the obvious issues still present.

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Facebook Polling Users About Privacy

I just completed an interesting two-question survey via an official link on Facebook.  The poll first asked to what extent, on a five-point scale from “completely disagree” to “completely agree,” I agreed with this statement: “Facebook cares about its users’ privacy and security.”  Next, Facebook asked if I would describe myself as:

  • Very open – I wouldn’t mind if everyone could see all of the information I share on Facebook
  • In between – I don’t mind if everyone can see some of my information, but certain information I only want to share with my close friends or family
  • Private – I only share things with people I know

The survey came from the Facebook Research Team.  I’m guessing the first question is not only to gauge people’s image of Facebook but a statistic to trumpet if most users answer positively.  (In light of Facebook’s naivete towards Platform privacy and security, I did not.)  The second question is interesting in light of Facebook’s shifts from more controlled/private to more open/public.  And as Bruce Schneier recently discussed in an essay on privacy salience, Facebook probably hopes most users fall into the “very open” category.

I certainly look forward to seeing the results of this survey if they’re released.

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Another Top Facebook Application Falls to Hacking

I can’t emphasize this enough: As the Facebook Platform is currently setup, nearly any XSS vulnerability in an application allows my hack from last month (I may need a name for this thing soon) to succeed.

Tonight, after two hours of poking around various applications, I once again successfully used my hack to access profile information via an XSS hole in an FBML application.  This particular application has over 10 million monthly active users.  It also luckily prevents a clickjacking install, but with such wide reach, a relaunch of the hack would affect many users anyway.

If any technology news site wants a great story on the security of the Facebook Platform, please get in touch – I simply want to get the word out on this issue to raise user awareness.

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Facebook Hack via FBML Application

I’d previously stated that I was confident I could relaunch my Facebook hack using an FBML application, but that I hadn’t worked out all the details.  Today, I successfully used an XSS hole in an FBML application to access profile information, just as I had done with canvas applications before.  I did so using an XSS vulnerability publicly published almost four months ago.

The particular application used this time always forwards new installs to the same URI, preventing me from using a clickjacking install to fully relaunch the attack page (though an added refresh may do the trick).  But it definitely proves the point that nearly any application with an XSS hole is vulnerable to this type of attack, including FBML applications.

For those who did not get to experience the hack when it was live, I’m including a screenshot of the results page for a fake Facebook profile.

Results page from Facebook attack under a fake profile.

Results page from Facebook attack under a fake profile.

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Understanding Koobface and other "Drive-By Download" type threats

Koobface is a classic “Drive-by Download” type of threat, which can be a difficult thing for anti-virus programs to deal with. The catch is that you’re being fooled into giving a program explicit permission to run. Should an anti-virus program second-guess that decision? Good question.
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A Few Clarifications

Why bother highlighting privacy problems on Facebook?  Isn’t privacy just an illusion anyway? With the way Facebook currently operates, users should probably assume that advertisers, developers, and hackers can access all of the information they post. However, most users are not aware of this, and fully believe in the privacy controls Facebook provides. Facebook needs to address privacy problems to match user confidence or better educate users on how easily others can access their data.

Hasn’t Facebook patched the holes that allow access to profile data? Those behind should be commended for the privacy hole they uncovered, which Facebook did patch. However, the privacy problems mentioned here remain unpatched. SuperPoke has patched the specific hole used in my demonstration hack, but other applications are still vulnerable to an identical attack.

Aren’t you simply highlighting problems in Facebook applications? Isn’t Facebook itself more secure? Mark it down: A vulnerability in a Facebook application is a vulnerability in Facebook itself. Since all applications are granted access to a wealth of user information and can perform many actions that directly affect a user, application holes can be exploited to the point of differing little from actually hacking a user’s profile.

Are these hacks really that serious if they require a user to click a special link? Hacks that do not require user intervention are certainly more powerful. However, many security researchers will affirm that getting a user to click on a link is not that difficult. Also, many of these hacks can work invisibly on what appears to be an otherwise harmless page. Finally, applications have many viral channels available to them, and these can be exploited by an application attack or a rogue application to compromise more users.

Doesn’t Facebook prevent advertisers from accessing personally identifiable information? For advertisements served by Facebook itself, the site does prevent such access. Unfortunately, several advertising networks for Facebook applications, such as SocialCash, can and do access personally identifiable information for targeting their ads. While this appears to be a clear TOS violation, Facebook has not shown interest in addressing this particular problem.  Two ad networks were shut down recently, but apparently for deceptive ads and not for the user information they accessed.

Can Facebook enable third-party applications at all and still enforce user privacy? Security researchers may disagree on this particular question, but I do think it clear that Facebook could do far more to protect user privacy. The Facebook Platform currently ignores important security techniques that have led to problems such as my recent application hacks. For example, allowing every application full access to user information contributes to making the hacks so serious.

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