Threat Description





A new variant of Doomjuice worm was found on 11th of February. This one also attacks against

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


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.


You may wish to refer to the Support Community for further assistance. You also may also refer to General Removal Instructions for a general guide on alternative disinfection actions.

Technical Details

Doomjuice.B is similar to to the original Doomjuice.A. This variant tries to improve the Distributed Denial-of-Service attack on The size of this variant is smaller, as Doomjuice.B does not contain or drop the source code of Mydoom.A.

System Infection

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

  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\NeroCheck
  • HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\NeroCheck

Distributed Denial-of-Service Attack

Doomjuice.B attacks via HTTP protocol like Doomjuice.A, but it tries to improve the Distributed Denial-of-Service attack. It sets random HTTP headers to make it more difficult to filter out the attack traffic:

User-Agent: Mozilla/4.0
 User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)
 User-Agent: Mozilla/4.0 (compatible; MSIE 5.0; Windows NT 5.0)
 Accept-Encoding: gzip, deflate
 Accept-Language: en
 Accept-Language: en-us

In addition, this variant starts 32-182 parallel threads to download the main page in an infinite loop, instead of the 16-96 of the previous variant.

The attack will trigger after 12th of February.

For more information on Doomjuice.A see:


Detection in F-Secure Anti-Virus was published on February 11th, 2004 at 10:09 GMT in update:
Database: 2004-02-11_01

Description Created: Mikko Hypponen and Katrin Tocheva February 11th, 2004
Technical Details: Gergely Erdelyi & Ero Carrera; February 11th, 2004


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