Virus Encyclopedia

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Threat LevelHigh threat
DistributionNot widespread
Common name:Mydoom.A
Technical name:W32/Mydoom.A.worm
Threat level:Medium
Alias:I-Worm/Novarg, WORM_MIMAIL.R W32/Mydoom@MM I-Worm/Novarg@MM

It launches Distributed Denial of Service attacks against the website It opens a port, allowing a hacker to gain remote access to network resources.

Affected platforms:

Windows 2003/XP/2000/NT/ME/98/95

First detected on:Jan. 27, 2004
Detection updated on:June 25, 2007
Proactive protection:
Yes, using TruPrevent Technologies
Repair utility:Panda QuickRemover

Brief Description 


Mydoom.A is a worm that spreads via e-mail in a message with variable characteristics and through the peer-to-peer (P2P) file sharing program KaZaA.

Mydoom.A launches DDoS (Distributed Denial of Service) attacks against the website if the system date is between February 1 and February 12, 2004. It does this by launching GET/ HTTP/ 1.1 requests every 1,024 milliseconds. On February 12, 2004, the worm finishes its payload, ending its execution whenever it is activated.

Mydoom.A drops the DLL (Dynamic Link Library) SHIMGAPI.DLL, which creates a backdoor, opening the first available TCP port in the range from 3127 to 3198. This backdoor component allows to download and run an executable file, and acts as a TCP proxy server, allowing a hacker to gain remote access to network resources.

Note: on February 10, 2004, a new variant of this worm was detected by PandaLabs. This new variant carries out the same actions as the original, but it is compressed

Visible Symptoms 


Mydoom.A is easy to recognize once it has affected the computer, as it opens the Windows Notepad and shows junk data.