Threat description



Randex (also known as SDBot) is a backdoor with network worm capabilities. This variant of Randex appeared on 28th of November 2003. It is functionally similar to previous versions, but has less features.


Automatic action

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

More scanning & removal options

More information on the 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

F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

Technical Details

The backdoor's file is a Windows PE executable 37376 bytes long. It is compressed with patched UPX file compressor.

When activated, the backdoor gets API addresses of different Windows functions and checks whether it is already installed on this computer. If not, the backdoor copies its file as 'msrundll.exe' to Windows System directory and creates a startup key for it in the Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]  "Microsoft Windows Kernel Functionalities" = "msrundll.exe"  [HKLM\Software\Microsoft\Windows\CurrentVersion\RunServices]   "Microsoft Windows Kernel Functionalities" = "msrundll.exe"    

After the backdoor starts, it tries to connect to an IRC server (one hardcoded name) and creates a bot in the specific channel (hardcoded name) on this server. Through this bot a hacker can control the backdoor's behaviour. A hacker can perform the following actions:

1. Log in and out of the bot (requires a password)  2. Terminate own process  3. Generate another random nickname for the bot  4. Connect, reconnect and disconnect from IRC server  5. Show bot status  6. Show bot ID  7. Show threads list  8. Show aliases list  9. Show log file  10. Start and stop sniffer functionality  11. Show network info  12. Show system information  13. Start and stop NTScan (spread to network)  14. Remove the bot  15. Delete the PAYLOAD,DAT file  16. Change bot's nickname  17. Join/part channels  18. Kill specific threads  19. Send SYN packets  20. Add aliases  21. Send private messages  22. Change channel mode  23. Join/part specific channel in a cycle  24. Update the backdoor  25. Start a specific file  26. Create clones  27. Download files  28. Show infected computer's IP address and connection type   

When instructed to do a NTScan, the backdoor copies itself to Windows System folder as 'ms093upd.dat', generates random IP addresses and tries to connect to them. The backdoor tries to retrieve network user names and connect using them, but in case this fails, it will try to connect as Administrator.

The backdoor uses the following passwords to connect to remote computers:

admin  root  1  111  123  1234  123456  654321  !@#$  asdf  asdfgh  !@#$%  !@#$%^  !@#$%^&  !@#$%^&*  Guest  Gast  Administrateur  server  Administrator  Beheerder  super  user  password  secret  xp  nt  me  love  girl  iloveyou  tits  pussy  2600  2800  hacker  leet  l337   

Once connected the backdoor tries to access to IPC$ share on remote computer and to copy itself to the following locations as 'MSL32.exe' and 'MSL3232.exe' files:

\Admin$\system32\MSL32.exe  \c$\winnt\system32\MSL3232.exe   

The above locations correspond to System32 folders of NT-based operating systems.

After copying its file, the backdoor creates a scheduled network task to start the copied infected file on remote computer. When this happens, a remote computer becomes infected with the backdoor.

F-Secure Anti-Virus already detects this worm generically as 'Backdoor.SDBot.gen'.

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