Even if you never connect your Facebook account to a single app, dozens of them may still have access to your profile information via your Facebook friends.
When your Facebook friends connect new apps, the list of permissions they approve can include access to not just their own information, but also specific information from your profile -- including your birthday, status updates, photos, hometown, current city and app activity.
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Facebook won't share information with your friends' apps that you haven't shared with your friends, and you can control which information friends' apps can access through a privacy settings page. But some Facebook users don't realize they're sharing information with app developers this way, or that they can control it.
How Apps Use Information From Your Friends
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Access to friends' information makes some Facebook-connected services more useful.
For instance, an app called Banjo, which alerts users when their friends are nearby, asks users to see Facebook friends' hometowns, locations, likes and education histories. It uses this information to figure out which friends are most relevant. Friends' information enables the app to be selective about when it sends alerts. A similar app called Glancee also asks for access to information on friends' profiles.
Christy Liu, co-founder of a travel recommendation engine called Wanderfly, tells Mashable relevance is also a factor in why that site asks for access to Facebook friends' information.
"Specifically, it helps us identify which friends you might want to follow and get recommendations from," she says. "For example, I might be more interested in travel recommendations from a friend who also lives in NYC than someone who lives in a small town somewhere across the world."
Some Facebook-connected services, such as recently launched people search engine Ark, base a large portion of their functionality upon access to your friends' profile information. Ark, for instance, lets uses search their own friends by criteria such as current city, gender, language, hometown or employer.
How to Control What Information Friends' Apps Can Access
Users can block their friends’ applications from accessing some information, but not everybody realizes these settings exist.
"It's hidden deep in Facebook," Israel-based entrepreneur Avi Charkham tells Mashable. "As a matter of fact, you can't even link directly to a page with those settings."
To raise awareness of this option, Charkham created a new website, which consists of just one link: the Facebook privacy setting for blocking friends' apps (he linked to the mobile version of the page).
Users can access this settings page on their own by opening their privacy settings, clicking "edit settings" next to "apps and websites," and then clicking the same option next to "How people bring your info to apps they use." Charkham's site just gives them a shortcut.
Providing a direct link seems like a small effort, but it has been well-received in the past. Earlier this year, Charkham made another website with shortcuts to app permission pages on popular social networks. The site took off. More than 200,000 people visited the site, and a link to it was retweeted more than 34,000 times.
"Most of all, it opened my eyes to how lost and helpless people feel when it comes to privacy," Charkham says of the simple site's popularity.
What You Won't Be Able to Control From the Privacy Settings Page
The only way to become completely invisible to friends' apps is to revoke all app access to your profile -- meaning you will no longer be able to play Facebook games or use apps. Otherwise, your name, profile picture, gender, networks and user ID as well as any information you make public on your profile is available to friends' applications.
Facebook notes this default in its statement of rights and responsibilities: “When you publish content or information using the Public setting, it means that you are allowing everyone, including people off of Facebook, to access and use that information, and to associate it with you (i.e., your name and profile picture).”
Facebook's Platform Policies, however, stipulate that "a user's friends' data can only be used in the context of the user's experience on your application," so applications aren't allowed to share information they learn about you via your Facebook friends with anyone but your Facebook friends -- who could technically access it anyway.
A Fair Trade?
To some, the exchange of some profile information for utility seems a fair one. Others, like Charkham, are offended by it. "It's basically 'outsourcing' my privacy to my friends and letting them decide who gets access to my private info," he says.
Are you grateful for the increased social capabilities that sharing information with Facebook friends’ apps provides, or will you be blocking such access? Let us know in the comments.
This story originally published on Mashable here.