Invasive micro-machines with the ability to regenerate and also to reconfigure other technology, individual nanobots are all but invisible. Ion attacks can disrupt and destroy them, and they are unable to penetrate force fields of any strength. Their radio signals can be jammed, in which case they have a back up light-pulse system that renders them visible in infrared, where they look like a swarm of Procyon fireflies.
Nanobot swarms require sustenance in a way, and are attracted to the CPUs of powerful computers which they will drain of CPU cycles in order to recharge themselves.