Backdoor.IRC.Bot

SUMMARY

Backdoor.IRC.Bot is a generic detection for a group of Backdoor Trojan Horses that uses IRC channels to launch Denial of Service (DoS) attacks, and that allows a hacker to control the compromised computer.

Protection

• Virus Definitions (LiveUpdate™ Weekly) May 7, 2003
• Virus Definitions (Intelligent Updater) May 5, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Medium
• Payload: Opens a back door to an IRC server to receive commands.
• Compromises Security Settings: Allows unauthorized access to a compromised computer.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.IRC.Bot is executed, it may create a copy of itself in the %Windir% or the %System% folders.

Note:

• %System% is a variable that refers to the System folder. By default this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
• %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows (Windows 95/98/Me/XP) or C:Winnt (Windows NT/2000).

In most cases, this Trojan uses one or more of the common loading points to ensure that it runs when you start Windows. For information about common loading points, read one of these documents:

• Common loading points of threats in Windows NT/2000/XP
• Common loading points of threats in Windows 95/98/Me

Some of the actions that Backdoor.IRC.Bot can perform include:

• Listening on an IRC channel for commands from a remote attacker, allowing them to control a compromised computer.
• Connecting through TCP port 6667 or 18067 to an IRC server.
• Viewing system information, such as running processes, software installed, and other items.
• Terminating processes.
• Flooding the IRC channels.
• Flooding mailboxes (mailbombing) .
• Executing programs and scripts on the compromised computer.
• Uploading or downloading the files to the compromised computer.
• Updating the version of the Trojan.
• Participating in a Distributed Denial of Service (DDoS) attack on a remote host.
• Searching files on the compromised computer.
• Executing commands on command.com.
• Scanning for computers with the LSASS vulnerability (described in Microsoft Security Bulletin MS04-011)
• Uninstalling the Trojan.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.

REMOVAL

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Run a full system scan and delete all the files detected as Backdoor.IRC.Bot.
4. Reverse the changes made to the Windows registry.
   

For specific details on each of these steps, read the following instructions.

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Note: The procedure described in this document is complex and assumes that you are familiar with basic Windows and DOS procedures. If you are not, then we suggest that you obtain the services of a qualified computer consultant.

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1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

• Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
• Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).
  
  The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Scanning for and deleting the infected files

1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
   • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan all files."
2. Run a full system scan.
3. If any files are detected as infected with Backdoor.IRC.Bot, write down the path and file names, and then click Delete.

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Note: If your Symantec antivirus product reports that it cannot delete an infected file, shut down the computer, turn off the power, and then wait 30 seconds. Restart the computer in Safe mode (Windows 95/98/Me/2000/XP) or VGA mode (Windows NT 4), and then run the scan again.

For instructions on restarting the computer in Safe mode, read the document, "How to start the computer in Safe Mode."

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4. Reversing the changes that were made to the registry

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WARNING: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

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1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. Refer to the list of infected files that you created while following the instructions in step c of the previous section, "Scanning for and deleting the infected files."
   
   In the right pane, look at the entries in the Name and Data columns. If you find an entry that refers to a file that was detected as infected, select the entry, press Delete, and then click Yes to confirm.
   
   
5. Do one of the following:
   • Windows NT/2000/XP: Skip to step g.
   • Windows 95/98/Me: Navigate to the key:
     
     HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion
     RunServices
     
     
6. Refer to the list of infected files that you created while following the instructions in the previous section. In the right pane, look at the entries in the Name and Data columns. If you find an entry that refers to a file that was detected as infected, select the entry, press Delete, and then click Yes to confirm.
   
   
7. Exit the Registry Editor.