1. A computer-implemented method for providing secure access to a computer, the method comprising: capturing a first image of a user with a camera at the computer in response to the user logging into a user account on the computer; extracting facial features from the first image; periodically detecting, after the capturing of the first image and while the user is still logged into the user account, whether a human face is in front of the computer, by capturing one or more lower-resolution images with the camera; capturing, after detecting that the human face is not in front of the computer, a second image with the camera at the computer, wherein the one or more lower-resolution images have a resolution lower than the first and second images; extracting facial features from the second image; comparing the facial features extracted from the second image with the facial features extracted from the first image; if the facial features extracted from the second image match the facial features extracted from the first image, then staying logged into the user account; and if the facial features extracted from the second image do not match the facial features extracted from the first image, then automatically logging out of the user account, wherein the user is logged into at least one personal account from the computer, wherein the at least one personal account is separate from the user account, and the method further comprises, if the facial features extracted from the second image do not match the facial features extracted from the first image, then automatically logging out of the at least one personal account.