Threat description




Randex is a network worm that has backdoor features. This variant of Randex appeared on 8th of September 2003.


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 worm's file is a Windows PE executable 73728 bytes long. The worm's file is not compressed. Some text strings in the worm are encrypted with a simple cryptoalgorithm.

When the worm's file is started it first looks for and deletes 'winnt32.dat' file in Windows System folder. Then the worm gets API addresses of different Windows functions and checks whether it is already installed on this computer. If not, the worm copies its file as 'netd32.exe' to Windows System directory and creates a startup key for it in the Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]  "Microsoft Network Daemon for Win32" = "netd32.exe"  [HKLM\Software\Microsoft\Windows\CurrentVersion\RunServices]   "Microsoft Network Daemon for Win32" = "netd32.exe"    

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

1. Log in and out of the bot  2. Display and clear masters list  3. Terminate own process  4. Generate another random nickname for the bot  5. Connect and disconnec from IRC server  6. List active threads  7. Show log file  8. Get connection type  9. Get system information  10. Start and stop NTScan  11. Uninstall the worm  12. Delete the WINNT32.DAT file  13. Terminate theads or a selected thread  14. Join and part from a channel, change bot's nickname  15. Open or run a specified file  16. Get DNS info  17. Open a specified URL  18. Perform SYN flood  19. Send private message from a bot  20. Create clones  21. Redirect traffic for specific port  22. Download files from a specified URL  23. Execute specified files  24. Change channel mode  25. Update the worm from a specified URL  26. Destroy current bot  27. Perform a DoS (Denial of Service) attack  28. Steal CD keys for the following games:    HalfLife  Unreal Tournament 2003  Battlefield 1942  Battlefield 1942: Road To Rome  Command and Conquer: Generals   

When instructed to do a NTScan, the worm copies itself to Windows System folder as WINNT32.DAT, generates random IP addresses and tries to connect to them. The worm tries to retrieve network user names and connect using them, but in case this fails, the worm will try to connect as Administrator. Once connected the worm tries to access to IPC$ share on remote computer and to copy itself to the following locations as NETD32.EXE file:

\ADMIN$\system32\netd32.exe  \C$\WINNT\system32\netd32.exe  

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

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


Detection of Randex.J worm was added in the following updates:

Detection Type: PC

Database: 2003-09-09_03

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