Threat Description



Aliases: Email-Worm.Win32.Atak.h,, I-Worm.Atak.h, Atak.h
Category: Malware
Type: Worm
Platform: W32


A new variant of the Atak worm was found on 15th of December 2004. The worm spreads in emails that have a subject "Merry X-Mas!" or "Happy New Year!".


Automatic action

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


Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.

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

Technical Details

When run the worm creates a mutex named "2k5" to avoid running more than once simultaneously.

The worm copies itself as:


where %WinSysDir% is Windows System folder, for example 'C:\Windows\System32\' on a default installation of Windows XP.

The worm adds an entry to the win.ini file using the Windows API call WritePrivateProfileStringA from the Kernel32.dll. The entry will look like this:

[windows]  run="%SysDir%\dec25.exe"   

As win.ini is not supported by Windows NT, 2000 and XP, on these operating system the changes will be added to the Registry. As as result Windows will start the worm on every time it boots.

Email spreading

Atak.h worm will collect e-mail address from files with certain extensions on all hard disks and RAM drives from C: to Z. Files with the following extensions will be checked:

.txt  .log  .html  .msg  .eml  .mht  .dbx  .asp  .php  .jsp  .htm   

The worm has its own SMTP engine which it uses to send infected emails. The messages sent by the worm will have one of the following subjects:

Merry X-Mas!  Happy New Year!   

The worm uses one of the following message body texts:

Happy New year and wish you good luck on next year!  Merry Christmas! Happy New Year! 2005 will be the beginning!   

The worm attaches itself to an infected message using a name combined of the following extensions:

.pif  .com  .bat  .scr.   

For example the name can be scr.pif or scr.scr. In some cases the worm can send itself in a ZIP archive.

Here's a screenshot of an infected message:


F-Secure Anti-Virus detects Atak.h worm with the following update:

Detection Type: PC
Database: 2004-12-15_01

Technical Details:Jarkko Turkulainen, December 15th, 2004


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