Symantec Norton Article

Antivirus Protection: Worms – The Most Dangerous Computer Virus

Viruses, Trojans and worms are the 3 common types of malware i.e. malicious software, and out of them the worms are the deadliest as they can function without any human intervention. Similar to viruses, worms also have capability to replicate themselves but are self contained i.e. they do not need a host program for propagation unlike viruses. Worms more commonly affect computer networks consisting of servers, routers and clients, even though they can cause damage similar to viruses like deletion of files, corruption of programs etc. Since the internet is just a large network of computer networks, it is very much susceptible to worm attacks.

Servers are powerful PCs with large storage capacity and store common resources that are shared by other PCs or clients in the network. Routers are used for routing network traffic and are nothing but specialized servers with customized operating system. Once released into a network, worms can replicate by themselves and hog the CPU time leaving little time for other programs to run. This leaves the network continuously busy and slows down network traffic.

Worms carry other types of malware called payloads with them. It can be spyware which surreptitiously monitors the activities of the computer or backdoor installation programs which act as hidden access points in the network and can be used to send spam or steal data or programs from the computer by hackers. MyDoom is a fast spreading worm discovered in January 2004. It was spread through emails containing the message ‘Andy, I’m just doing my job, nothing personal, sorry’. The creator of the worm was never identified but it is believed to be directed at the website of the company Santa Cruz Operation (SCO), in order slow down traffic to the website. It soon spread to other internet sites slowing down the entire internet considerably.

The worm’s payload can cause considerable damage to a computer in a network by switching off antivirus functions, opening up computer ports etc. The latter can allow data transfer to computers outside the network or delete files stealthily.

De-worming

Firewalls are designed to control network traffic and can act as shield to computers in the network by effectively cloaking them. They are reasonably effective in saving computer from worm attacks. However, worms can be distributed through emails as attachments and hence caution should be exercised when opening mail from unknown sources or unexpected files from a known source. Despite all precautions, worms may get into your system whose symptoms are slowing down of internet access, automatic reboots or sluggishness of the system. If any of these symptoms are noticed, the computer should be scanned by antivirus software immediately. If it does not help, instruction manuals on the internet could consulted for effective de worming.