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Backdoor:W32/IRCBot.ST


Discovered:
Aliases:


August 13, 2006
Backdoor.Win32.IRCBot.st

Malware
BackdoorWorm
W32

Summary

A remote administration utility which bypasses normal security mechanisms to secretly control a program, computer or network.



Disinfection & Removal

Automatic Disinfection

Allow F-Secure Anti-Virus to disinfect the relevant files.

For more general information on disinfection, please see Removal Instructions.



Technical Details

IRCBot.ST (also known as Mocbot) is the first variant of this IRC backdoor-worm to use the recently discovered MS06-040 exploit to spread itself. When a hacker initiates a scan within a defined range of IP addresses, the backdoor attempts to connect to the selected IP addresses and deliver the exploit to those computers. If a remote computer is vulnerable, then it becomes infected with the backdoor.

After being run, the backdoor installs itself to the system, modifies several security settings, attempts to connect to a remote IRC server, and starts listening for commands from a remote hacker.

The backdoor's file is a Windows PE executable, 9609 bytes long, packed with MEW file compressor and patched with PE_Patch. The backdoor's code has an additional encryption layer (simple XOR).


Installation

After the backdoor's file is run, it creates a mutex with the name "wgareg". This is done to prevent running more than one copy of the backdoor on the system.

The backdoor also checks for the service with the name "wgareg" and if it's active, it skips the installation phase. During its startup phase, the backdoor creates a thread that checks for active debuggers and terminates the backdoor's process if a debugger is detected.

Just before exiting, the backdoor encrypts its code with the same subroutine it used to decrypt at startup.

During the installation phase, the backdoor copies its file to the Windows System folder (usually named C:\Windows\System32\ by default) with the wgareg.exe name and then creates a service for that file with the following name and description:

  • Windows Genuine Advantage Registration Service

This service ensures that the user's Microsoft Windows operating system is genuine and registered. Stopping or disabling this service will result in system instability.

The backdoor then changes several settings in the Registry including those, related to Windows Security Center and Firewall.


Activity

Once active, the backdoor attempts to connect to one of the following remote IRC servers on TCP port 18067:

  • bniu.househot.com
  • ypgw.wallloan.com

The backdoor generates a random nickname and joins a password-protected channel, #n1, and waits for commands from a channel operator. A remote hacker who is controlling the backdoor can do any of the following:

  • Start any files located on the remote (infected) computer
  • Update the backdoor's file from the Internet
  • Disable and uninstall the backdoor
  • Find files on the remote (infected) computer
  • Create a remote command shell
  • Flush the DNS cache
  • Send commands to an AIM (AOL Instant Messenger) window
  • Connect to a different IRC server
  • Create a simple proxy
  • Perform an SYN flood
  • Perform a DDoS (Distributed Denial of Service) attack
  • Spread to vulnerable computers using the MS06-040 exploit

Registry Modifications

Sets these values:

  • [HKEY_LOCAL_MACHINE\software\microsoft\ole] "enabledcom"
  • [HKEY_LOCAL_MACHINE\system\currentcontrolset\control\lsa] "restrictanonymous" "restrictanonymoussam"
  • [HKEY_LOCAL_MACHINE\system\currentcontrolset\services \lanmanserver\parameters] "autoshareserver"
  • [HKEY_LOCAL_MACHINE\software\microsoft\security center] "antivirusdisablenotify" "antivirusoverride" "firewalldisablenotify" "firewalldisableoverride"
  • [HKEY_LOCAL_MACHINE\software\policies\microsoft\windowsfirewall \domainprofile] "enablefirewall"
  • [HKEY_LOCAL_MACHINE\software\policies\microsoft\windowsfirewall \standardprofile] "enablefirewall"


Detection

F-Secure Anti-Virus detects this malware with the following updates:

Detection Type: PC
Database: 2006-08-13_01





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