Facebook has recently added a security feature that makes it impossible for a hacker, or more simply someone unauthorized to access your account, from hiding their "secret logins" into your account. You now have access to a log of recent login history in your profile settings, called "Login Activity", which lists the last successful login to your account, as well as any other sign in activity for other computers and devices which are still logged into your Facebook account (either because they recently signed in, or because they have checked the "Remember me" option when they clicked on the Login button). Facebook will give you the date and time ("timestamp") for each occurrence, the estimated location, and the web browser and operating system used by the remote computer or mobile internet device. This tutorial explains how to access this information, and we'll show you how to get the IP address of people who try to login to your account (since these are not included in the recent login activity log).
First, login to your Facebook account (the one for which you want to check recent login activity, that is). Then, click on "Account" near the top right corner, and choose "Account Settings". You'll be redirected to the "My Account" screen: if needed, select the "Settings" tab at the top (should be selected by default).
Tip: in our experience, Facebook does update the recent login activity right away ("in real time"); if you suspect someone from accessing your account and do not see any sign in log for it, try a few minutes later, just to be on the safe side!
And, to clarify any confusion: this tracker updates the login history only when a device actually needs to manually sign into your account; not when it comes back to Facebook without having to login (i.e., with the "remember me" option enabled).
If you don't recognize one of the computers or devices currently connected to your Facebook account, just click on the corresponding "end activity" link: Facebook will remove the entry to that particular device from your recent login history, and remotely logout the device (same process as when you manually sign out from your Facebook account). The person will never know, or receive any kind of scary notice - they'll simply need to log back in. If this was not one of your devices, or not someone you authorized, we recommend that you immediately change Facebook password (ideally do it before logging out intruders!)
Tip: looking at your login activity will not show the IP address (though this is the information on which Facebook bases its "sign in location" guesses). But if you setup login notifications, Facebook will send you the time, location, and IP address of any new computer or device who logs into your Facebook account.