Backdoor.Anakha

SUMMARY

Backdoor.Anakha is a backdoor Trojan horse that allows a hacker to use Internet Relay Chat (IRC) to gain control of a computer. It also opens TCP/UDP ports to allow a hacker to take control of the system. Backdoor.Anakha is written in the Microsoft Visual Basic programming language and is compressed with ASPack.

NOTE: Virus definitions dated prior to June 27, 2002, may detect this threat as Backdoor.Trojan.

Protection

• Virus Definitions (LiveUpdate™ Weekly) July 3, 2002
• Virus Definitions (Intelligent Updater) June 28, 2002

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 50 - 999
• Number of Sites: More than 10
• Geographical Distribution: Medium
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low
• Payload Trigger: Running the trojan
• Payload: allows a hacker to take control over the system
• Compromises Security Settings: It allows unauthorized control of a compromised system.

Distribution

• Distribution Level: Low
• Ports: random changed

TECHNICAL DETAILS

When Backdoor.Anakha runs, it does the following,

It copies itself as C:\%System%ShellEx.exe.

NOTE: %System% is a variable. The Trojan locates the WindowsSystem folder (by default this is C:WindowsSystem or C:WinntSystem32) and then copies itself to that location.

To allow itself to run when Windows starts, the Trojan adds the value

ShellEx  C:\%System%ShellEx.exe

to the registry key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun

It also creates a text file named C:\%System%Rundll32.pin.

NOTE: C:\%System%Rundll32.pin itself is not viral, and therefore Norton AntiVirus does not detect it. We recommend that you delete this file manually if your computer was infected with this Trojan.

Backdoor.Anakha then opens some randomly changed TCP/UDP ports to allow a hacker to connect to the computer. It allows a hacker to perform a wide variety of actions on the compromised computer. The action can be any of (but not limited to) the following:

• Manage the installation of the backdoor
• Perform DoS attacks against a target that is defined by the hacker
• Send information about the compromised computer to the hacker
• Listen for IRC commands from the hacker
• Control the IRC client on the compromised computer
• Download and upload files to or from the compromised computer

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

1. Update the virus definitions, run a full system scan, and delete all files that Norton AntiVirus (NAV) detects as Backdoor.Anakha.
2. Delete C:\%System%Rundll32.pin.
3. Delete the value
   
   ShellEx  C:\%System%ShellEx.exe
   
   from the registry key
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun

For details on how to do this, read the following instructions.

To scan with Norton AntiVirus and delete the infected files:

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
   • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
     
     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. Start Norton AntiVirus (NAV), and make sure that it is configured to scan all files.
   • NAV Consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • NAV Enterprise products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
3. Run a full system scan.
4. Delete all files that NAV detects as Backdoor.Anakha.
5. (Optional) Using Windows Explorer, delete C:\%System%Rundll32.pin.

To remove the value from 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 only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

1. Click Start, and 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 value
   
   ShellEx  C:\%System%ShellEx.exe
   
5. Click Registry, and click Exit.