Term: Worm

Definition: a worm is a script, which means that the recipient does not have to run an executable file/attachment in order to be infected. Just receiving the file is enough. It's possible for a worm to attack without you ever opening the email message. It can come into your system through the preview pane. This is why I recommend turning off the preview pane in Outlook. If you simply must know what's there, configure your Inbox to give you the first few lines as a synopsis. It's not a cure-all, but it helps.

Example: According to Symantec, the current plague called the MyDoom virus is actually the W32.Novarg.A@mm "mass-mailing worm that arrives as an attachment with the file extension .bat, .cmd, .exe, .pif, .scr, or .zip.

"When a computer is infected, the worm will set up a backdoor into the system by opening TCP ports 3127 through 3198, which can potentially allow an attacker to connect to the computer and use it as a proxy to gain access to its network resources. In addition, the backdoor can download and execute arbitrary files.

"The worm will perform a Denial of Service (DoS) starting on February 1, 2004. It also has a trigger date to stop spreading on February 12, 2004. These two events will only occur if the worm is run between or after those dates. While the worm will stop spreading on February 12, 2004, the backdoor component will continue to function after this date."

MyDoom generates its mass emailings using a "spoofed" From field, which means it may appear to come from people you know. Unfortunately, the subject line and message text are both randomly generated by the worm. This makes it difficult to spot.

Discussion: In the past, worms tended to be relatively harmless to your computer, limiting themselves to error messages and occasional shut-down of machines. They were more an irritation than a threat. But, as you can see, they are becoming more virulent and will soon undoubtedly become as destructive as viruses and trojans.

Note: If after you update your virus protection files you discover you have the MyDoom worm on your system, you can download a MyDoom removal tool from Symantec's website.