It started when a USB flash drive infected by a foreign intelligence agency was left in the parking lot of a Department of Defense facility at a base in the Middle East. It contained malicious code and was put into a USB port from a laptop computer that was attached to United States Central Command.
The cyber spent nearly 14 months cleaning the worm, named agent.btz, from military networks. Agent.btz, a variant of the SillyFDC worm, has the ability "to scan computers for data, open backdoors, and send through those backdoors to a remote command and control server."