Net-Worms propagate via computer networks. The distinguishing feature of this type of worm is that it does not require user action in order to spread.
This type of worm usually searches for critical vulnerabilities in software running on networked computers. In order to infect the computers on the network, the worm sends a specially crafted network packet (called an exploit) and as a result the worm code (or part of the worm code) penetrates the victim computer and activates. Sometimes the network packet only contains the part of the worm code which will download and run a file containing the main worm module. Some network worms use several exploits simultaneously to spread, thus increasing the speed at which they find victims.