1. A method, comprising: capturing images periodically from a camera on a computing device; comparing each of the captured images to a stored image of an authorized user; determining that one of the captured images does not match the stored image of the authorized user; locking the computing device, upon determining that one of the captured images does not match the stored image of the authorized user; and when each of the captured images contains images of multiple users, determining whether none of the multiple users in each of the captured images matches the stored image of the authorized user, and locking and preventing further operation of the computing device by each user of the multiple users in each of the captured images, upon determining that none of the multiple users in each of the captured images matches the stored image of the authorized user.