Summary

Sdbot.RPC.A is an IRC controlled backdoor which contains spreading routines exploiting the MS03-026 (also known as DCOM/RPC) vulnerability.

Disinfection

Disinfection solution for SdBot backdoors is deleting or renaming their files. We recommend to use the latest version of F-Secure Anti-Virus to disinfect SdBot backdoors.

If the infection is in a local network, please follow the instructions on this webpage:

http://www.f-secure.com/v-descs/netdisinf.shtml

Additional Details

System infection

After entering the system Sdbot.RPC.A installs itself with the following steps:

1, Copies the worm to the System Directory as 'winlogin.exe'

2. Adds 'winlogin.exe' to the registry to the following value

 'HKLM\Software\Microsoft\Windows\CurrentVersion\Run\NDplDeamon'

3, Drops the main DLL component to the System Directory as 'yuetyutr.dll'

4, The DLL is loaded into the running explorer.exe process

4, Modifies system.ini:

 [Boot]
 Shell=explorer.exe winlogin.exe

5, Adds several values to the registry:

 'HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce\winlogon'
 'HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\winlogon'

Backdoor

The backdoor code is based on Sdbot. It connects to a predefined IRC server and joins a channel and waits for commands. Commands it supports provide full access to the compromised computer.

With one of the commands the backdoor can be instructed to scan for vulnerable hosts using the DCOM/RPC exploit. If a vulnerable host is found Sdbot.RPC.A infects the host.

More information on the DCOM/RPC (MS03-026) vulnerability is available at

http://www.microsoft.com/technet/security/bulletin/MS03-026.asp

Detection

Detection in F-Secure Anti-Virus was published on August 13th, 2003 in update:

[FSAV_Database_Version]
Version=2003-08-13_01



[Analysis: F-Secure Anti-Virus Research Team; 13th of August, 2003]

Description Updated: Alexey Podrezov, September 10th, 2004;