Would you unleash a worm on your networks if that worm was designed to protect the networks instead of infiltrate them? Dave Aitel thinks you would, and that was the subject of his presentation at the latest Hack in the Box conference in Malaysia.
Aitel has already developed a working model that can create beneficial worms (which he calls nematodes) and thinks that eventually the concept will evolve into new security products that you'll want to purchase. You can view the slides from his presentation, which are available in a PDF file. You might also read this interesting story , which discusses nematodes in some amount of detail.