Cybermat

Cybermats were small cyborgs used by the Cybermen. They had poisonous bites which could turn Humans into Cyberslaves.

History
When the Doctor and Amy arrived in the Arctic Circle, they discovered Cybermats turning people into Cyberslaves in order to help awaken an army of Cybermen. They were able to repel the Cybermats using a special frequency on a sonic amplifier device. (VG: Blood of the Cybermen)