On the internet, privacy is virtually nonexistent. But even if you take precautions to avoid posting private information online, you might be giving away more than you realize, according to The New York Times.

Researchers at Carnegie Mellon were able to figure out the Social Security numbers of nearly five million people born in the United States from 1989 to 2003, using data from social networking profiles and other public information available on the internet. Websites like Facebook and Twitter are potential mines of information that computers will increasingly be able to collect from for purposes of recreating someone’s identity. Unfortunately, opting for privacy controls on your Facebook account or Twitter profile can’t completely protect you. People you chat with online often unwittingly give away details of your private life by referring to your school, gender or hobbies, for example.

In the meantime, the best way to protect your privacy on a social network is to act as if you’re in public. Be discreet when chatting with friends, and try to avoid giving away specific names or locations unless necessary. E-mail and instant messaging are two modes of online communication that are not visible to the general public (although precautions are still recommended), so they might be better to use when you want to send your friends pictures or party invitations.