Dumping friends on Facebook helps make you secure

WORRIED about loose-tongued friends sharing your private details with the world? Culling the least discreet members of your social network will help you feel more secure, but it's not a perfect solution. What if your best friend is an offender?

Google's social networking site, Google+ had been running for less than a week when it turned out there was nothing to stop your friends "resharing" posts with the entire internet. Google now lets users disable reshares, but the problem is indicative of how little control you have over what your friends do.

Pritam Gundecha at Arizona State University in Tempe has a technique for working out which friends are most likely to leak private information so you can remove them, if you choose. Gundecha examined the relative importance of data 2 million Facebook users elect to share with the world and calculated the privacy risks friends pose to each other.

For example, around 80 per cent of users are happy to disclose their gender, but less than 1 per cent share their home address. That suggests people publicising their address aren't particularly privacy-conscious and you might want to avoid them.

Using these statistics, the researchers gave each user a vulnerability score and worked out which friends will cause your vulnerability score to go down should you unfriend them.

It turns out that unfriending the least discreet friend increases your security by an average of more than 5 per cent - worth it for a casual acquaintance, but perhaps not so easy if your best buddy is a blabbermouth. "There are some friends you cannot remove, irrespective of their vulnerability," admits Gundecha. While the existing technique doesn't take this kind of social importance into account, he is now working on a version that does. The preliminary work will be presented at the Knowledge Discovery and Data Mining conference in San Diego, California this week.

Randy Baden at the University of Maryland says unfriending people based on how vulnerable they make you is an intriguing take on the problem. But he adds that the vulnerability scores are "based on how much potential there is for someone to leak information, not whether that person actually is leaking information".