Item from Call of Duty: Modern Warfare III by Infinity Ward / Activision
The cyberwarfare payload that Makarov uploaded to London's train network — Konni Group's escalation from physical operations to infrastructure warfare, and the mechanism for the final MW3 mission.
The Trojan Horse virus is Makarov's demonstration of what the Ultranationalist movement intends after the ground campaign. Taking a capital city's infrastructure and making it a weapon — that's the scale of ambition he's operating at. The 141 chased the hacker carrying it through London public spaces, acquired the flash drive after killing the buyer, and then discovered the upload had already completed. The mission became a damage-limitation exercise, which is what fighting Makarov always eventually becomes.
A data file on a flash drive. In the physical world, it looks like nothing — a piece of hardware small enough to lose in a pocket. Its presence in London's train control system is invisible until the moment Konni activates it, at which point every train in the network is under their control.
Also known as: Trojan Horse, Makarov's Virus