The owner of an American computer software maintenance company was arrested for sabotaging software used by the U.S. Navy to track the location of warships and subs. Among other things, the software insured that there were no collisions with commercial shipping. The arrested man, owner of Ares Systems International, was upset over being rejected when he bid on another navy contract. In response, he put code in navy systems he had access to, that would shut down navy networks in the future. After the first two systems went down, last May, investigators were able to figure out what caused the failure. That led navy investigators to Ares Systems International, and the arrest of the firms owner.
This kind of sabotage is usually thought of as coming via an Internet connection. But most of the computer mischief is traced to insiders. Protecting against this sort of thing is more difficult. The inside jobs don't get as much attention, but they continue to be the source of the most damage.