Worm Viruses, Deadliest Of All

Of the three most common types of malware (malware is short for malicious software, i.e. designed to harm) - viruses, Trojans and worms - the latter is the most harmful because only worms can function without human intervention.

Worms, like viruses, replicate themselves but unlike viruses are completely self-contained. Viruses need a 'host program' to spread, but worms propagate independently.Though they can be designed to do the same kind of harm (file deletion, program corruption, etc), worms usually affect networks. Networks operate by means of servers and routers. The Internet is just a large set of mutually cooperating public computer networks.

Servers are similar to PC's, though usually faster and with more storage and other resources. They 'serve' other systems by making those resources available to multiple users. Routers are just specialized servers, typically of different hardware and operating systems, used to route network traffic. Hence the name.

Worms can be released into a network and their self-replication behavior causes damage. Since routers use memory, processor time, etc worms - like viruses - can overwhelm them, causing them to slow down and become unstable. Viruses don't have to delete files to do harm, they can cause the CPU - central processing unit, used to run programs - to be constantly busy. That leaves no resources for other programs to run.

Worms often carry 'payloads' - other types of malware such as spyware or backdoor installation programs. Spyware is used to monitor your computer activities and backdoors are hidden access points to your computer which can be exploited by hackers to send spam or steal data from your computer.