Reliable transmission over covert channels in first person shooter multiplayer games

We propose and evaluate a novel improvement to a previously published, unreliable covert channel based on the network traffic of multiplayer, first person shooter online games (FPSCC). Covert channels typically embed themselves within pre-existing (overt) data transmissions in order to carry hidden messages. FPSCC encodes covert bits as slight, yet continuous, variations of a player's character's movements. These variations are visually imperceptible to human players, yet occur frequently enough to create a low bit-rate covert channel. The nature of first person shooter network protocols means the original FPSCC channel is noisy (not reliable), experiencing a significant number of bit errors (including synchronisation errors). We have now augmented FPSCC to ensure bits are transmitted reliably. Evaluation of our technique with a prototype demonstrates throughput of up to 13 bits/second without any bit errors.