Something that I thought of that I am sure I am probably not the first to come up with is the concept of an anti-trojan bot. Such a virus would seek out and destroy bad viri/trojans while being harmless and benign in itself. I wonder if this has ever been tried. It would be kind of a "white blood cell" in the computing world. Perhaps a variant could be written to disable spam producing or trojan spreading systems that are known to be causers of malware on people's systems..... just a thought..... any ideas on this concept?