The invention relates to a system and method for preventing a protected computing device from executing unauthorized processor commands. A data entry database of the system stores encoded data entered by a human user as data entry events. A command verification module of the system implements an authentication algorithm for determining whether a processor command to be executed by the computing device originates from a trusted source. The command verification module determines the trustworthiness of a processor command as a function of parameters of the processor command, which include an association of the command with one or more of the data entry events. Determination can also be made based on other processor command parameters, such as the type of processor command and/or contextual parameters of the processor command. Upon making the determination, the command verification module allows authenticated processor commands to be executed and prevents non-authenticated processor commands from being executed by the computing device.