Threat description




NOTE: A new variant, Doomjuice.B has been found. See:

Doomjuice worm, also known as Mydoom.C, was found on February 9th, 2004. It infects machines which are already infected by Mydoom.A. It does not spread over email at all.

Doomjuice worm does not attack but it tries to perform a Distributed Denial-of-Service attack on

F-Secure monitors the ongoing Mydoom-related attacks in our Weblog:


Automatic action

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

More scanning & removal options

More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.

You may also refer to the Knowledge Base on the F-Secure Community site for more information.

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Technical Details

Network Propagation

Doomjuice spreads between computers that are already infected with the Mydoom.A worm. It uses the backdoor installed by Mydoom.A. To locate machines with the backdoor open, Doomjuice scans random IP addresses by trying to connect to TCP port 3127. If the port is open the worm sends itself in a specially crafted package that makes the Mydoom.A infected machine to execute the file thus infecting it with Doomjuice too.

System Infection

After entering the system Doomjuice copies itself to the Windows System Directory as 'intrenat.exe'. The copy is added to the registry as

  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\Gremlin
  • HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\Gremlin
Distributed Denial-of-Service Attack

After the 8th of February the starts a DDoS attack against Between 8th and 12th of February the worm will wait for up to 365 seconds. After the 12th it will start the attack right away.

In order to overload the worm starts 16-96 parallel threads that connect to the web site and try to download the main page in an infinite loop.


One of Doomjuice's payloads is that it drops the source code of Mydoom.A in a bzip2 compressed TAR archive. The file is dropped the root of all hard drives and the user's profile directory as 'sync-src-1.00.tbz'.


Detection in F-Secure Anti-Virus was published in update:

Detection Type: PC

Database: 2004-02-09_04

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