Threat Descriptions

Kelvir.f

Classification

Category :

Malware

Type :

Worm

Platform :

W32

Aliases :

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.

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 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.

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