Since Facebook launched, the social network has constantly been adding new functions and features that ensure users can maintain their privacy and keep their accounts secure. Among these features are the ability to enable two-step authentication and view active sessions. Facebook also offers an alert service that will notify you should someone log-in to your account using a device that you've never used before. Here's how to enable login notifications in Facebook
Log into your Facebook account and from the drop down menu next to Home, select Account Settings.
Select Security from the far left-hand side of the window. Now click on the section marked Login notification.
You'll be given the choice of either an email or a text message/push notification as an alert to notify you when your account has been accessed from a computer or mobile device that you haven't used before. Check the box next to which method of notification you prefer. It's worth noting you can tick both if you want. Now press Save Changes.