What is a Worm Virus? - Definition, Examples & Removal Tools

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  • 0:00 What Is a Worm Virus?
  • 1:13 Well-Known Examples of…
  • 2:53 Removal Tools
  • 4:18 Lesson Summary
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Lesson Transcript
Instructor: Lonny Meinecke

Lonny teaches psychology classes at King University, and has a bachelor's degree in IT and a doctorate in psychology.

This lesson will explain what a worm virus is and how it differs from other computer attacks. You'll see some examples and learn about tools to remove a worm virus, then take a brief quiz to reinforce this new information.

What Is a Worm Virus?

Before diving into the definition of a worm, we should define the term computer virus. A computer virus is a carefully hidden piece of computer code that has the ability to spread from one system to another. A virus can do significant damage, or at least it may become a nuisance and interrupt productivity. Like a virus that spreads between human beings, a computer virus spreads between machines. But a computer virus is not actually alive; it's a piece of executable code that spreads because it is attached to a computer file. So, wherever the file goes, the virus goes with.

A worm virus is very similar and is often categorized as a sub-class of computer virus. One main difference between the two is that a user must perform an action for a virus to keep spreading, whereas a worm does not require human intervention to spread. Once a worm enters your system, it sort of scouts the environment looking for opportunities, such as emailing itself to everybody in your contact list. So, the key differentiating characteristic of a worm virus is that it can replicate itself, almost as though it were a biological virus.

Well-Known Examples of Worm Viruses

There are countless examples of worm viruses, some of which you may be familiar with. They became more prominent with the rise of the Internet. For instance, the Michelangelo worm had a long run in the 1990s, infecting computers for about six years. A computer would be infected without the user even knowing; that is, until March 6, the birthday of the famous artist after whom the worm was named. On this date, it would engage with the operating system, overwriting computer storage devices and making them unusable. News of the Michelangelo worm actually caused a panic. Considering the damage in terms of lost productivity and billions in lost profits, panic is an understandable response.

In 2000, the ILOVEYOU worm was spread as an email attachment. Clicking the attachment resulted in an infection, rather than an expression of affection. This infection could overwrite most of the data on the infected computer. Another worm began to spread soon after: Code Red was released in 2001, and it exploited a weakness in a popular Microsoft Web server.

The all-around worst, though, was MSBlast. Spread during 2003, it is said to be the most damaging, malicious software in history. It resulted in the infection of 25 million computers, a nightmare for Microsoft's tech support center, which had to deal with three million callers within five days of MSBlast's release. Eventually, it led to the arrest and imprisonment of at least one person. The one who was imprisoned only wrote a minor variant of it, and the original author or authors remain at large.

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