Threat Descriptions

Backdoor:W32/IRCBot.BNZ

Classification

Category :

Malware

Type :

Backdoor

Platform :

W32

Aliases :

Backdoor:W32/IRCBot.BNZ

Summary

IRCBot.BNZ is a backdoor. It can be instructed to scan for vulnerable target machines, update itself, as well as download and execute arbitrary files.

Removal

Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

This IRCBot connects to an IRC server at fixed.milan-fans.com at port 2233 for instructions.

A backdoor is a trojan that allows unauthorized access to a computer system. It is a remote access tool that allows a hacker to gain access to a compromised computer through the "back door" that the trojan has opened (usually a TCP or UDP port).

Usually a backdoor is a standalone file that installs itself to the system after it is run and then remains active in the memory listening on specific network ports for commands from the remote host.

IRCBot.BNZ is downloaded from malicious sites. This download can be initiated by a shellcode executed via an unpatched MS04-011 vulnerability on target machines.

When first run copies of the malware will be created in %WINDOWS%\System32\spool.exe as and C:\%name%.exe where %name% is a random six-digit number.

Note: %WINDOWS% represents the default Windows installation folder.

Launchpoints/Autostart:

IRCBot.BNZ uses the following registry entries to run on startup:

  • HKCU\Software\Microsoft\Windows\CurrentVersion\RunMicrosoft Update = "C:\WINDOWS\system32\spool.exe
  • HKLM\Software\Microsoft\Windows\CurrentVersion\RunMicrosoft Update = "C:\WINDOWS\system32\spool.exe

Changes the following registry entries:

  • HKLM\Software\Microsoft\OleEnableDCOM = "N"
  • HKLM\System\CurrentControlSet\Control\Lsarestrictanonymous = "1"
  • HKLM\Software\Microsoft\Windows NT\CurrentVersion\WinlogonShell = "EXPLORER.EXE\%name%.exe

Note: %name% represents the name of the file previously dropped by the malware.

Backdoor Functionality:

IRCBot.BNZ has IRC backdoor functionality. With this functionality a remote attacker may:

  • Download and execute arbitrary files
  • Scan for vulnerable ports on target machines
  • Attempt to infect a target vulnerable machine
  • Update the bot on the infected machine

IRCBot.BNZ uses an MS04-011 LSASS exploit to inject and execute shellcode on the target machine. Please refer to the following Microsoft website for details on the vulnerability and solutions.

  • http://www.microsoft.com/technet/security/bulletin/MS04-011.mspx

Payload

IRCBot.BNZ may download a file from www.[REMOVED].net/c8563/staff.exe which as of February 22, 2008 is a copy of the same malware.