1. One or more non-transitory computer readable media having computer readable instructions stored thereon for user authentication at a computing device, the instructions when executed by a processor direct the computing device to: display a plurality of objects on a display screen, the plurality of objects comprising objects that are part of a passcode, the passcode comprising a plurality of objects; generate a plurality of trigger signals at set intervals; in response to each trigger signal, cause an image sensor to capture an image; analyse each image to, determine a direction of gaze; determine the object on the display screen that corresponds to the direction of gaze; and determine whether the object that corresponds to the direction of the gaze matches an object in the passcode; and after the images have been analysed, determine if a threshold for matches has been exceeded and if the threshold has been exceeded indicate positive authentication.