1. A computer-implemented method of authenticating a user of a computing device, comprising: capturing video information over a determined period of time using a video camera of the computing device; locating a head portion of the captured video information corresponding to a head of the user; analyzing, using at least one processor of the computing device, the head portion using a facial recognition algorithm to attempt to determine an identity of the user; monitoring, using the at least one processor, a red chroma color component of the head portion relative to at least one other chroma color component or luminance value over the determined period of time; and authenticating the user when the identity of the user is determined to correspond to an authorized user and when the red chroma color component varies with a frequency and amplitude consistent with a living human face.