Smibag

Summary

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Smibag is a multi-component worm that attempts to send itself using a localized version (Korean) of MSN messenger. The worm is sent as SMB.EXE file. The worm drops adware components to an infected hard drive.

Removal

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Automatic action

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

More

More information on 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

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Technical Details

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The SMB.EXE file that is send via MSN Messenger is a dropper. Inside it contains a ZIP archive and a decompression utility. When the dropper is run, it drops UZ.EXE and EXT.ZIP files and runs UZ.EXE utility to decompress the archive.

The archive contains the following files:

admagic.exe - adware file  atl.dll     - legitimate Windows component  msnvc.exe   - file that sends the worm via MSN Messenger  raw32x.dll  - data file  sm.dll      - browser helper object file   

The ADMAGIC.EXE file is then copied to the root of C: drive together with the dropper (SMB.EXE file). After that the UZ.EXE, ATL.DLL, RAW32X.DLL and SM.DLL files are copied to Windows System directory and the SM.DLL and ATL.DLL files are registered to Windows with Regsvr32.exe utility.

When the ADMAGIC.EXE adware file is run, it creates a startup key for itself in System Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]  "svchost" = "c:\admagic.exe"   

This file is supposed to open Internet Explorer every 5 minutes. But we did not observe this behaviour on our test system. The file has a few adult website links in its body.

The worm attempts to spread using MSN Messenger as SMB.EXE file. The file that does the actual sending is MSNVC.EXE.

Detection

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F-Secure Anti-Virus detects Smibag worm with the update released on October 1st, 2003:

Detection Type: PC
Database: 2003-10-01_01

Description Details: 1st of October, 2003