Threat description




Funner is a MSN worm that spreads by sending itself to the contacts listed in Microsoft's Windows Messenger.


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.

Contact Support

F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

Technical Details

When executed, Funner will copy itself to the WINDOWS directory under the name rundll32.dll and alter registry entries to ensure the worm is started. It will also copy itself under WINDOWS SYSTEM directory as


The following registry keys are altered to ensure the worm runs upon next reboot

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run "MMSystem"

 "c:\winnt\rundll32.exe "c:\winnt\system32\mmsystem.dll"", RunDll32"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run "MMSystem"

 "c:\winnt\rundll32.exe "c:\winnt\system32\mmsystem.dll"", RunDll32"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon "Userinit"


Funner also overwrites the local hosts file with a file containing various URLs.

NOTE! There is Windows system DLL named rundll32.dll under WINDOWS SYSTEM directory. This DLL is part of Microsoft Windows operating system.


F-Secure Anti-Virus detects Funner since the update published on October 11th, 2004:

Detection Type: PC

Database: 2004-10-11_01

Submit a Sample

Suspect a file or URL was wrongly detected? Send it to our Labs for further analysis

Submit a Sample

Give And Get Advice

Give advice. Get advice. Share the knowledge on our free discussion forum.

More Info