For some time now, Facebook has offered two-factor authentication that allows you to force the entry of a code whenever there is a log-in attempt from an unrecognized device. This is a very good additional layer of protection against unauthorized log-ins to a user’s account. When you consider that most people use weak, easily guessable passwords (despite my advice and the advice of other experts), this additional factor can make a big difference.
Setup is simple: Go to Account > Security, edit Login Approvals and check the box. Facebook then gives you a wizard that walks you through setting up your mobile phone, starting with their sending of a confirmation code. Enter the code and you’re done!