Backdoor.IRC.RPCBot.G

SUMMARY

Backdoor.IRC.RPCBot.G is an Internet Relay Chat (IRC) Trojan horse. It allows an attacker to control your computer through IRC. It is also a worm that can use the DCOM RPC vulnerability (described in Microsoft Security Bulletin MS03-026) to spread itself.

Protection

• Virus Definitions (LiveUpdate™ Weekly) October 8, 2003
• Virus Definitions (Intelligent Updater) October 8, 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
• Compromises Security Settings: Allows unauthorized remote access.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.IRC.RPCBot.G runs, it performs the following actions:

1. Copies itself as %System%Mshtml.exe.
   
   
2. Adds the value:
   
   "Win32 Process Host"="mshtml.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   so that the Trojan runs when you start Windows.
   
   
3. Adds the value:
   
   "Win32 Process Host"="mshtml.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion
   RunOnceEx
   
   so that the Trojan runs when you start Windows.
   
   
4. Adds the value:
   
   "Win32 Process Host"="mshtml.exe"
   
   to the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersion
   RunOnce
   
   so that the Trojan runs when you start Windows.
   
   
5. Adds the value:
   
   "Shell"="Explorer.exe mshtml.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWinlogon
   
   so that the Trojan runs when you start Windows NT/2000/XP.
   
   
6. Adds the value:
   
   "Userinit"="C:WINDOWSsystem32userinit.exe,C:WINDOWSsystem32mshtml.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   
7. Adds the value:
   
   "Directory"="C:WINNTSystem32..."
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTFTPD
   Parameters
   
   
8. Adds the value:
   
   "Win32 Process Host"="svchost.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   InitDLLProc
   
   
9. Adds the value:
   
   "Initial"="1"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   InitDLLProc
   
   
10. Connects to the specified IRC servers and joins a channel to listen for commands from its creator.
    
    
11. Allows its creator to perform any of the following actions:
    
    • Control the IRC client on a compromised computer.
    • Scan IP addresses.
    • Terminate remote processes.
    • Perform Denial of Service (DoS) attacks against targets that the creator of this threat selects.
    • Exploit the DCOM RPC vulnerability: The worm generates random IP addresses. Once the IP addresses are generated, the Trojan sends specially formed data, which exploits the DCOM RPC vulnerability, to that particular IP address.
    • Download files from predefined Web sites.
    • Download a Security Patch for the Blaster Worm from Microsoft.

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.RPCBot.G.
4. Delete the values that were added to the registry.

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

1. To disable 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. To update 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. To scan for and delete 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.RPCBot.G, click Delete.
   

4. To delete the values from the registry

---

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. In the right pane, delete the value:
   
   "Win32 Process Host"="mshtml.exe"
   
   
5. Navigate to the key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion
   RunOnceEx
   
   
6. In the right pane, delete the value:
   
   "Win32 Process Host"="mshtml.exe"
   
   
7. Navigate to the key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersion
   RunOnce
   
   
8. In the right pane, delete the value:
   
   "Win32 Process Host"="mshtml.exe"
   
   
9. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWinlogon
   
   
10. In the right pane, delete the value:
    
    "Shell"="Explorer.exe mshtml.exe"
    
    
11. Navigate to the key:
    
    HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
    
    
12. In the right pane, change the value:
    
    "Userinit"="C:WINDOWSsystem32userinit.exe,C:WINDOWSsystem32mshtml.exe"
    
    to
    
    "Userinit"="C:WINDOWSsystem32userinit.exe,"
    
    
13. Navigate to the key:
    
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTFTPD
    Parameters
    
    
14. In the right pane, delete the value:
    
    "Directory"="C:WINNTSystem32..."
    
    
15. Navigate to the key:
    
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
    InitDLLProc
    
    
16. In the right pane, delete the value:
    
    "Win32 Process Host"="svchost.exe"
    
    
17. Navigate to the key:
    
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
    InitDLLProc
    
    
18. In the right pane, delete the value:
    
    "Initial"="1"
    
    
19. Exit the Registry Editor.