MyDoom

MyDoom is a computer virus, designed to reach the computer through an e-mail that is accompanied by a file attachment, most commonly one with an .exe, .scr, .zip or .pif file name extension. The subject line varies, and often makes the e-mail appear as an error message. If the attached file is opened, the worm installs malicious code on the computer user's system and sends copies of itself to all contacts in the user's address book. There are many variations of the worm, which was allegedly designed to attack the Web site of the SCO Group Inc., the small software maker suing IBM over the use of software code used for the Linux operating system. Also known as Novarg or Shimgapi, the worm could allow attackers to gain unauthorized access to an infected computer and use the computer to aid in an Internet attack to bring down SCO's Web site. Mydoom.B also reportedly blocks access to some websites, including Microsoft.com and some antivirus vendors' websites. Users who received the worm and simply ignored or deleted it were able to avoid any damage.

MyDoom was first spotted in January 2004, and it infected more than one million computers in its first few days. In July, a variant of the worm shut down Google for several hours. A new variant, which spreads in part through e-mail addresses found by using search engines, was detected in February 2005.

For more information, see Symantec Security Response: MyDoom.

Last updated: February 18, 2005.