Facebook has launched a new "login approvals" feature that can further secure your Facebook account. This adds a second step to the login process if you try to access Facebook from an unrecognised device.
The login approvals feature can be turned on in Facebook under your Account settings under Account Security. You'll need your mobile phone on hand so you can get the text message with a code to authenticate your computer.
This looks like an update Facebook has made to its two-factor authentication mentioned just last month. Extra security features like this help secure your account in the event a hacker gets hold of your username and password, because they'll have to authenticate via the security code sent to your mobile phone before getting in. If you lose your phone, you can log back into Facebook from any device you previously authorised and then change your security password and settings.