Methods, systems, and computer programs are presented for securing a computing device. One security device includes a processor, memory and a connector. The memory includes a computer program that, when executed by the processor, performs a method. The method includes operations for detecting that the connector is coupled to a second computing device, and for determining a user associated with the security computing device. In addition, the method includes operations for receiving periodic images from an image capture device coupled to the second computing device, and for performing continuous authentication operations to validate an identification of the user based on the periodic images. The user is disabled from using the second computing device after an authentication operation fails.