I think the most dangerous "tool" or however you are putting it would probably be the person themself. Knowledge (or the lack of it) is the most dangerous tool anywhere, in any field. Why would you consider backdoor trojan programs the most dangerous? If you you use a good antivirus or a trojan cleaner regularly you won't have anything to worry about on that side. Try securing your computer. Run netstat and see which ports are open on your computer and what services are running. If you want to stomp these risks out (BO2k, Sub7, etc) , install Linux. Why do you want to know what are the most dangerous anyway? It makes no sense and sounds a little fishy to me. My 2 cents.

Exitrial