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.