what motivates a person to write a virus. I was giving a talk to some sixth form students about the way that computing and the internet has changed our world in a single generation, and afterwards one of the boys starting asking me about viruses. He seemed just a little too keen to know the technicalities, and eventually admitted that he wanted to write one. He obviously hadn't given much thought to the havoc he might cause, so I stayed around and chatted to a group of them for a while. It seemed to me that quite a few of these boys (none of the girls seemed interested) thought the idea of creating an enormous amount of confusion and chaos was appealing - they liked the thought that they would probably never be caught, and that they could boast about their exploits to their mates.
Whether or not they were typical of virus writers as a whole I don't know, but I imagine they were. Most of the culprits we see caught appear to be young and male, and I imagine most of them do it to prove they can. I doubt that many of them have the faintest idea about the trouble their brainchild might cause.