Systems, methods and program codes are provided wherein an analyzer analyzes input from a terminal device; ascertains human-like behavior; and terminates an active session, generates a time-out warning, manipulates an idle session timer or presents a challenge in response to a humanness likelihood determination or to a challenge result. In one aspect a keystroke analyzer and a command sequence analyzer determine whether the terminal device input is likely from a human user or from an automaton. In another aspect a Completely Automated Public Turing Test to tell Computers and Humans Apart challenge is presented. Timing characteristics include maximum generation rate, burstiness, and keystroke sequence delays, and command characteristics include a no-action-required characteristic and a query characteristic. A command sequence analyzer may have an affinity for a command line interface. Weighting algorithms or artificial intelligence routines may be applied to humanness likelihood outputs.