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How Facebook, Social Networks Leak Your Privacy

An article in the Boston Globe yesterday demonstrated how social networks like Facebook can “leak” privacy.

Devising a simple algorithm, two MIT students came up with a method for analyzing a person’s network on the social networking website Facebook. They discovered that they could fairly reliably determine whether a man was gay or not by the friends he kept, regardless of whether he identified his sexual orientation on Facebook:

Using data from the social network Facebook, they made a striking discovery: just by looking at a person’s online friends, they could predict whether the person was gay. They did this with a software program that looked at the gender and sexuality of a person’s friends and, using statistical analysis, made a prediction. The two students had no way of checking all of their predictions, but based on their own knowledge outside the Facebook world, their computer program appeared quite accurate for men, they said. People may be effectively “outing” themselves just by the virtual company they keep.

The method was not reliable for lesbians or bisexuals.

What this episode demonstrates is not so much the expertise of the MIT students, but the “leakiness” of the information we provide to social networking websites. Even when we don’t explicitly state facts about our life (e.g., diagnosed and being treated for major depression for 2 years), such characteristics may be discovered simply by other indications in our online profiles (friending Psych Central, for instance, and being a member of a Facebook depression support group).

Every passing month, our online lives become more and more entangled with our real lives — we no longer have separate online personas (and when we think we do, researchers can usually discover our real identity with enough searching). Social networking websites like Facebook, while offering a the powerful and usually-positive ability to interconnect with our friends and acquaintances, also tells the world more about us than perhaps we intended.

And that’s the key takeaway — we’re sharing more information than we had intended or meant to share because of social network analysis. While perhaps providing some potential insights into human behavior for researchers, its unintended consequences suggest that our lives are being mined for data. While this analysis is nothing particularly new in the marketing world, websites like Facebook take such analysis to a new level.

The project, given the name “Gaydar” by the students, Carter Jernigan and Behram Mistree, is part of the fast-moving field of social network analysis, which examines what the connections between people can tell us. The applications run the gamut, from predicting who might be a terrorist to the likelihood a person is happy or fat. The idea of making assumptions about people by looking at their relationships is not new, but the sudden availability of information online means the field’s powerful tools can now be applied to just about anyone.

For example, Murat Kantarcioglu, an assistant professor of computer science at the University of Texas at Dallas, found he could make decent predictions about a person’s political affiliation. He and a student – who later went to work for Facebook – took 167,000 profiles and 3 million links between people from the Dallas-Fort Worth network. They used three methods to predict a person’s political views. One prediction model used only the details in their profiles. Another used only friendship links. And the third combined the two sets of data.

The researchers found that certain traits, such as knowing what groups people belonged to or their favorite music, were quite predictive of political affiliation. But they also found that they did better than a random guess when only using friendship connections. The best results came from combining the two approaches.

When used for academic research, such efforts seem harmless. But what’s to stop a company from using these types of analysis for individual, investigative research? Imagine, for instance, large insurance companies compiling complex and complete profiles on individuals — including what their social networks say about their health and mental health — in seconds by using such analysis, and then setting your insurance rates accordingly? Or a background checking firm providing not only their usual basic background information on an individual, but a whole page of “inferred” information from such analyses? It could readily jeopardize careers, job advancement, and maybe someday, even romantic relationships (“Click here to understand what your date’s Facebook profile really says about them and their likely interest/compatibility with you!”).

This isn’t something most people think about (much less agreed to) when they signed up for Facebook or another social network. Surprisingly, social networks like Facebook don’t place any limits on people mining their network for such data. And while it seems harmless right now, history has shown us the many ways such tools can be used and abused for other people’s interests over our own.

There is a way to stop this from happening to you — set your profile to “private,” so only people you specifically choose can see your information.

Read the Globe article: Project ‘Gaydar’: An MIT experiment raises new questions about online privacy

Read the Mind Hacks entry about additional social network analysis: Unweaving the tangled web

How Facebook, Social Networks Leak Your Privacy

John M. Grohol, Psy.D.

Dr. John Grohol is the founder of Psych Central. He is a psychologist, author, researcher, and expert in mental health online, and has been writing about online behavior, mental health and psychology issues since 1995. Dr. Grohol has a Master's degree and doctorate in clinical psychology from Nova Southeastern University. Dr. Grohol sits on the editorial board of the journal Computers in Human Behavior and is a founding board member of the Society for Participatory Medicine. You can learn more about Dr. John Grohol here.

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APA Reference
Grohol, J. (2018). How Facebook, Social Networks Leak Your Privacy. Psych Central. Retrieved on September 28, 2020, from
Scientifically Reviewed
Last updated: 8 Jul 2018 (Originally: 21 Sep 2009)
Last reviewed: By a member of our scientific advisory board on 8 Jul 2018
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