Worms aren't just for dogs anymore. Find out how to inoculate your computer against these nasty parasites.

What Are Worms?

Worms are descended from viruses and are even nastier. Just as ever stronger doses of pesticide breed ever more resilient locusts, better and better anti-spyware software bred ever more devious viruses.

Finally, some virus designers stopped having their creations infect and take over files the way real viruses infect and take over cells. Instead, they created programs that could stand on their own and cause plenty of trouble without the help of any other software applications. Just worms are independent organisms that can infect a host directly, so do computer worms infect computers directly.

What Do Worms Do?

Worm designers are often even more sinister than virus designers, since worm designers are not just vandals. Worm designers often use their creations to achieve specific goals:

Backdoor creation. Worms often try to set up another kind of malware, a backdoor. A backdoor is a hidden opening in your network connection that lets the worm send data out and take data in. Practically speaking, the data it's sending out are often spam emails, and the data it takes in are instructions on spam emails to send.

Denial of service attack. Some worm designers really are vandals rather than profit-hungry con artists sending spam. But their vandalism can be more targeted. They use worms to send out numerous requests to remote computers, such as web servers, in order to overwhelm them and therefore shut them down. This is called a denial of service attack.

Spyware, Trojan, adware, and virus installation. Worms are often used simply to unleash other forms of malware on a computer that might otherwise block them.

Information theft and fraud.Worms can multitask in order to set up spyware that gathers sensitive information--often financial information--and then set up backdoors, Trojans, viruses, or dialers to disseminate the stolen data.

How Do Worms End Up on a PC?

Worms enter PCs just as viruses, spyware and other malware do: any way they can! Some favorite points of entry for worms:

Websites can actually download software to your computer without you realizing it. This software includes not only worms, but also spyware, adware, viruses, and other malware. These malware programs find their way into websites either by the deliberate design of the site owner or because hackers have installed the software on the website's server.

Peer-to-peer file-sharing networkscontain many nice-enough-looking files that are really worms. One of the sneakiest disguises is a filename that indicates the spyware is really a video of a beautiful actress.

Email, the favored route of viruses, can still be exploited by Spyware. But since new email programs usually block the automatic opening of file attachments, this is less of a problem than it used to be.

Any internet connection inevitably lets data flow both in and out, and so is vulnerable to attacks by worms.

How Do You Get Rid of Worms?

There's really only one good way to make sure your computer is rid of worms: scan it with multiple antivirus and anti-spyware programs using a full-system scan. Worms are tricky, so anything less than a full-system scan might let them escape. Worse, with new worms coming out all the time, some antivirus and anti-spyware packages may not even know about a new worm until after its wreaking havoc on your machine. That's why you should try using more than one antivirus program and more than one anti-spyware program to increase your odds of successfully detecting the malware.

Don't have more than one anti-spyware and antivirus software? You'd better start downloading. After all, worms won't take excuses.