Why do hackers create computer viruses? What's their motive?

[Scepcop]

Why do hackers create computer viruses constantly as though it were some kind of business to them? What's the gain or motive? What's in it for them? It makes no sense.

Why don't they put their skills into creating something to sell to make money, or working as a computer programmer or software engineer and getting paid?

Is there any conspiracy behind this? Why can't law enforcement just stop the problem for good and arrest all the perpetrators?

[Arouet]

Actually, from what I understand one of the best ways to get a job in computer security is to become a well known hacker then switch over to the other side when they hire you to stop your former compatriots!

I think most start off just as rebellious kids who have some skills and like the challenge and thrill of hacking. Some have political motivations and target particular companies, governments, etc.

As for stopping them: it's hard! Hackers do get caught, but remember, these are for the most part anomymous, smart people skilled at covering their tracks.