Think your roommate's been using your computer while you're not around, but don't have any proof? Worried your little brother or significant other is snooping through your stuff? Here's how to check on both Windows and Mac OS X so you can catch and confront anyone who's logging onto your computer without your permission.
In Windows, you can enable logon auditing so that it keeps track of both successful and failed attempts. Once it's turned on, it will record the username and the time of the logon. You can find instructions for enabling it here.
Once it's turned on, you can see the information in the Event Viewer, which tells you what your computer's been up to recently. To open it, click on the Windows key in the bottom left corner and type "event viewer" into the search bar.
From here, open Windows Logs. Under the Security tab, you'll be able to see everything that's been done on your computer. You can double-click on any event to see details. Any event tagged with the number 4624 is a successful logon.
On a Mac, you can check by seeing when your computer was last woken from sleep mode. First, open Console by pressing Command + Spacebar or clicking the Spotlight icon to search for it. By typing "wake" into the search bar and scrolling to the bottom of the list, you can see the most recent events.
There are different wake reasons to tell you what caused the computer to come out of sleep mode. You can also search from the command line by typing the following:
Obviously this only works if you put your computer to sleep when you leave, but it's a good idea to do so anyway. And, as usual, it's a better idea to password protect your computer so someone can't logon just by waking it up.
Do you know of any other tricks to see if anyone's used your computer? Or how about more details about what they've been up to? Be sure to share them in the comments.