Randex is a network worm that has backdoor features. This variant of Randex appeared on 8th of September 2003.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
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:
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
Technical Details: Alexey Podrezov; 11th of September, 2003