Backdoor.IRC.Ratsou.D

SUMMARY

Backdoor.IRC.Ratsou.D is a Backdoor Trojan horse that gives an attacker full access to a compromised computer.

This Backdoor Trojan horse consists of multiple files, which the Ratsou.exe file installs. Ratsou.exe is approximately 1.2 MB in size.

Protection

• Virus Definitions (LiveUpdate™ Weekly) April 1, 2004
• Virus Definitions (Intelligent Updater) April 1, 2004

Threat Assessment

Wild

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

Damage

• Damage Level: Low

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.IRC.Ratsou.D is executed, it performs the following actions:

1. Creates the folder, %Windir%System32DriversDsdn36, and inserts the following files in that particular folder:
   
   

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   Note: %Windir% is a variable. The Trojan locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.

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   • Aim.dll (A nonmalicious text file)
   • Aim.txt (A nonmalicious text file)
   • C.dll (Detected as Backdoor.IRC.Ratsou.D)
   • Crazy.exe (Detected as Backdoor.IRC.Ratsou.D)
   • Empavms.exe (A Hack tool that is used to hide windows. Symantec antivirus products that support security risks detect it as Hacktool.Hidewindow.)
   • Flood.ocx (Detected as Hack tool.Flooder)
   • Ipservers.dll (A nonmalicious text file)
   • Java.dll (Detected as Backdoor.IRC.Ratsou.D)
   • Libparse.exe (A nonmalicious file)
   • Lsass.exe (Detected as Backdoor.IRC.Ratsou.D)
   • Miconfig.exe (Detected as Backdoor.IRC.Ratsou.D)
   • Moo.dll (A nonmalicious file)
   • Msccl.dll (Detected as Hack tool.Flooder)
   • Msconig.exe (A nonmalicious file)
   • Newuser.bat (Detected as BAT.Trojan)
   • Nhtml.dll (A nonmalicious file)
   • Regedit.dll (Detected as Backdoor.IRC.Ratsou.D)
   • Remote.ini (Detected as Hack tool.Flooder)
   • Restart.exe (A nonmalicious file)
   • Sipg.ocx (Detected as Backdoor.IRC.Ratsou.D)
   • Start.ocx (Detected as Backdoor.IRC.Ratsou.D)
   • Sysboot.dll (Detected as Backdoor.IRC.Ratsou.D)
   • Sysconfig.ocx (Detected as Backdoor.IRC.Ratsou.D)
   • Syste32.dll (Detected as IRC Trojan)
   • Temp (A nonmalicious text file)
   • Unicod_look (A nonmalicious file)
   • Unicod_ready (A nonmalicious file)
   • Users.dll (Detected as Backdoor.IRC.Ratsou.D)
   • Wincmd35.bat (Detected as BAT.Trojan)
   • Wind.dll (Detected as IRC Trojan)
     
     
2. Inserts the following files in the %System% folder.
   
   

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   Note: %System% is a variable. The Trojan locates the System folder and copies itself to that location. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).

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   • explorer.dll (Detected as Backdoor.IRC.Ratsou.B)
   • iexplore.dll (Detected as Hacktool.Rootkit)
     
     
3. Adds the values:
   
   "HID.EXE"="%windir%system32dsdn36lsass.exe"
   "lsass"="%windir%system32dsdn36lsass.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   so that this patched mIRC program runs when you start Windows.
   
   
4. Hooks the IRC file extensions in:
   
   HKEY_LOCAL_MACHINESoftwareClasses
   
   which call %Windir%System32Dsdn36lsass.exe when chat files are opened.

Once this Trojan is running on the system, it will contact an IRC server on TCP port 6667, and then join a predefined chat channel. This will allow the attacker to control an infected computer.

Also, this Trojan may open TCP port 31337.

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. Restart the computer in Safe mode or VGA mode.
4. Run a full system scan and delete all the files detected as Backdoor.IRC.Ratsou.D.
5. Reverse the changes made to the registry.
   

For 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"

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Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

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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 restart the computer in Safe mode or VGA mode
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.

• For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
• For Windows NT 4 users, restart the computer in VGA mode.
  

4. 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.Ratsou.D, click Delete.

5. To reverse the changes 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. In the right pane, delete the values:
   
   "HID.EXE"="%windir%system32dsdn36lsass.exe"
   "lsass"="%windir%system32dsdn36lsass.exe"
   
   
5. Exit the Registry Editor.
   
   
6. Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."

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Note: If you use mIRC, you may need to re-install it.

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