Kelvir.f

Classification

Malware

Worm

W32

Kelvir.f, IM-Worm.Win32.Kelvir.f

Summary

Kelvir.f is a worm that uses MSN Messenger to send out a link. The link points to a site that contains self-extracting file which will install Kelvir.f and a new Sdbot variant.

Removal

To get rid of this worm it is enough to delete its files from the infected hard disk. The latest versions of F-Secure Anti-Virus can automatically disable (rename) the worm's infected files. If automatic disinfection fails, please select 'Delete' disinfection action for the worm's files when it is detected. Instructions are here:

https://support.f-secure.com/enu/home/virusproblem/howtoclean/howtodeleteinfec...

Please restart a computer after disinfection.

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

Find out more

Knowledge Base

Find the latest advice in our Community Knowledge Base.

User Guide

See the user guide for your product on the Help Center.

Contact Support

Chat with or call an expert for help.

Submit a sample

Submit a file or URL for further analysis.

Technical Details

The self-extracting file is a PE executable, about 76K long. When run, it will create the Worm's folder:

C:\Program Files\RWNT3\

and place two files in there:

Fart.exe -- 19337 bytes long

rwnt3.exe -- 6778 bytes long

It will also drop copy of the Sdbot into %SYSTEM% directory. Then the worm will alter registry entries to ensure that the Sdbot is activated upon reboot. There is no entry that activates Kelvir.h after the system is restarted.

HKCU\Software\Microsoft\Windows\CurrentVersion\Run\
 "Microsoft MSN Services" = "MSts32.exe"
 HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\
 "Microsoft MSN Services" = "MSts32.exe"
 HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices\
 "Microsoft MSN Services" = "MSts32.exe" 

FSAV detects the dropper as component: Backdoor.Win32.SdBot.gen