Linux.Mare.K

SUMMARY

Linux.Mare.K is a worm that spreads by exploiting vulnerabilities. The worm opens a back door and then downloads and executes remote files on the compromised computer.

Protection

• Virus Definitions (LiveUpdate™ Daily) March 15, 2006
• Virus Definitions (LiveUpdate™ Weekly) March 15, 2006
• Virus Definitions (Intelligent Updater) March 15, 2006
• Virus Definitions (LiveUpdate™ Plus) March 15, 2006

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
• Payload: Downloads and executes files.
• Compromises Security Settings: Opens a back door on TCP port 80.

Distribution

• Distribution Level: Low
• Ports: TCP port 80

TECHNICAL DETAILS

When Linux.Mare.K is executed, it performs the following actions:

1. Attempts to open a back door on TCP port 80 and connect to two predetermined IP addresses.
   
   
2. May receive the following commands through the back door from attackers:
   
   
   • Update the worm
   • Execute files
   • Terminate the worm
     
     
3. Downloads and executes the following executable file from the above IP addresses:
   
   listen
   
   Note: The location of the downloaded file will depend on the folder in which the worm was executed. This location of this folder will depend on the location of the WWW and PHPBB folders on the compromised computer.
   
   
4. Download the following file, which is an updated version of the program, if the above file already exists on the compromised computer:
   
   update.listen
   
   
5. Logs its activities to the following file:
   
   
   listen.log
   
   
6. The worm attempts to exploit the XML-RPC for PHP Remote Code Injection Vulnerability (as described in Bugtraq ID 14088) and the Mambo Open Source Multiple Input Validation Vulnerabilities (as described in Bugtraq ID 11220).
   
   
7. If successful, the worm downloads and executes the following files from predetermined IP addresses:
   
   
   • cacat (detected as PHP.Backdoor.Trojan)
   • cmd.gif (detected as Trojan Horse)
     
     
8. The downloaded files are copies of other threats and may attempt to download and execute the following files:
   
   
   • r (detected as Backdoor.Kaitex)
   • curios (detected as Linux.Mare)

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

If your Symantec antivirus product detects Linux.Mare, delete the infected files.

Once the threat attacks a computer, it is difficult to determine what else the computer has been exposed to. In most cases, changes other than those made by the threat will not have occurred. However, the author of the threat may have been able to use the threat to access the computer to make changes to it. Unless you can be absolutely sure that malicious activity has not been performed on the computer, we recommend completely reinstalling the operating system.