The basic behavior that classifies a program as a worm is self-replication and automatic distribution. Some worms do nothing more than to make and distribute copies of themselves. A “payload” is anything a worm does in addition to this basic behavior. A worm that is “payload-free” is one that does nothing more than copy and distribute itself. While seemingly not as menacing as other types of worms, payload-free worms are still problematic because as they spread they can consume massive amounts of network and computer resources causing computer and networks to slow down and eventually crash.