Facebook Security Tips
Facebook launched new security features to protect users from spam, malicious attacks and privacy violation.
Now Facebook allows you to approve the devices you commonly use to log in and then to be notified by email or text message whenever your account is accessed from a device you haven't approved.
Try it out by going to "Account Security" on the Account Settings page.
When we see that someone is trying to access your account from an unusual device, we'll ask the person to answer an additional verification question to prove his or her identity as the real account owner. For example, we might ask the person to enter a birth date, identify a friend in a photo or answer a security question if you've previously provided one. These questions are designed to be easy for you, and hard for a bad guy, and we've already seen some great results.
via Facebook's blog