Backdoor.Kol

SUMMARY

Backdoor.Kol is a Backdoor Trojan that gives an attacker unauthorized access to a compromised computer. The Backdoor is controlled via commands issued by the hacker through several IRC channels. Backdoor.Kol is a Delphi application, packed with ASPack v2.11.

Protection

• Virus Definitions (LiveUpdate™ Weekly) March 19, 2003
• Virus Definitions (Intelligent Updater) March 14, 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
• Modifies Files: Modifies system registry.
• Compromises Security Settings: Allows unauthorized access to the compromised machine.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.Kol runs, it performs the following actions:

1. Copies itself as one of the following randomly chosen file names:
   
   • %Windir%Loader32.exe
   • %Windir%Mstask32.exe
   • %Windir%WinIPM.exe
     
     NOTE: %Windir% is a variable. The Trojan locates the primary Windows installation folder (by default this is C:Windows or C:Winnt) and uses it as a destination folder.
     
2. Creates one of the following randomly chosen registry values so that the Trojan runs when you restart Windows:
   
   • Dynamic Link Library loader    %windows%Loader32.exe
     
     in the registry key
     
     HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
     
   • Microsoft Task Manager     %windows%mstask32.exe
     
     in the registry key
     
     HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
     
   • Windows IP Monitor     WinIPM.exe
     
     in the registry key
     
     HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
     
3. Connects to an IRC server, joins several specific channels, and waits for commands that the hacker transmits through IRC. The commands allow the hacker to perform any of the following actions:
   
   • Deliver system information to the hacker
   • Download and execute files

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. Update the virus definitions.
2. Do one of the following:
   • Windows 95/98/Me: Restart the computer in Safe mode.
   • Windows NT/2000/XP: End the Trojan process.
3. Run a full system scan, and delete all files that are detected as Backdoor.Kol.
4. Reverse the changes that the Trojan made to the registry.
   

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

1. 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 here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

2. Restarting the computer in Safe mode or ending the Trojan process

Windows 95/98/Me
Restart the computer in Safe mode. All Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document "How to start the computer in Safe Mode."

Windows NT/2000/XP
To end the Trojan process:
1. Press Ctrl+Alt+Delete once.
2. Click Task Manager.
3. Click the Processes tab.
4. Double-click the Image Name column header to alphabetically sort the processes.
5. Scroll through the list, and look for the following names:
   • Loader32.exe
   • Mstask32.exe
   • WinIPM.exe
     
6. For each process that you find, click the name, and then click End Process.
7. Exit the Task Manager.
   

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.Kol, click Delete.

4. Reversing the changes made to the registry

CAUTION: Symantec strongly recommends that you back up the registry before you make 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.

1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type regedit and then click OK. (The Registry Editor opens.)
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the following value(s) if they exist:
   
   Dynamic Link Library loader   %windows%Loader32.exe
   Microsoft Task Manager     %windows%mstask32.exe
   Windows IP Monitor     WinIPM.exe
   
5. Exit the Registry Editor.