Facebook Rolling out New Security Features

The requirement to enter information that only you would know — such as the identity of your friends — can help stop unauthorized access should your password somehow become compromised.

To get notified when someone accesses an account from a new computer or device, you have to turn that feature on. To do this, go to "account settings," scroll down to "account security," then click "change." There, you can choose to be notified of log-ins by e-mail or text message.

Facebook is asking users to activate, or "opt-in" to, the security setting, even as it takes an "opt-out" approach with some of its marketing and personalization features. With opt-out, participation is automatic unless the user takes action.

Without giving an exact figure, Facebook says only a tiny percentage of its users have their accounts compromised. But a small percentage of 400 million can still be sizable.

The site's users are a good target for cybercriminals because of the implicit trust people place in Facebook. They are more likely to respond to scams and other messages that appear to come from real friends, but are actually sent by hackers able to game the system.