Threat Descriptons



Category :


Type :


Aliases :

TrojanProxy.Win32.Mitglieder.T, W32/Bagle.M, I-Worm.Bagle.m, Mitglieder.T


Worm:W32/Bagle.M drops a variant of Trojan-Proxy:W32/Mitglieder on an infected computer. The worm has no replication routine; instead it is distributed to new victims by trojan-proxies.


For removal instructions specific to Bagle infections, see Email-Worm:W32/Bagle.

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 worm's file is a PE executable about 14336 bytes in size packed with UPX file compressor.

Bagle.M was first reported on March 11th, 2004


When first executed, the worm copies itself as


to the Windows System folder and creates a startup key for this file in the Registry:

  • [HKCU\Software\Microsoft\Windows\CurrentVersion\Run] "usrgtway.exe" = "%winsysdir%\SYSWRUN4X.EXE"

where %winsysdir% represents Windows System folder name.

The worm then drops 2 more files into the Windows System folder:


Both files are DLLs (Dynamic Link Libraries).

The WINDLLZUP.EXE is a loader for BGXTDLL.EXE file. It allows both files to become DLLs used by EXPLORER.EXE file (one of the main Windows components). The BGXTDLL.EXE file is a new variant of Mitglieder proxy trojan.


Once installed and activated, the Mitglieder trojan-proxy generates a random number in order to select a port it can use to listen for remote commands and use as a mail relay. The port number selected is always larger than 2000.

The trojan connects to 2 sites in the .INFO domain to report the infected machine's IP address and proxy port. It also connects to 2 sites to download a list of banned IP addresses that the proxy will ignore.

Additionally, the trojan tries to kill processes that belongs to certain anti-virus and security software.

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