Linux.Mare

SUMMARY

Linux.Mare is a worm that spreads by exploiting the PHP-Nuke "phpbb_root_path" Arbitrary File Inclusion vulnerability. The worm, which has back door capabilities, also downloads and executes remote files on the compromised computer.

Protection

• Virus Definitions (LiveUpdate™ Weekly) December 28, 2005
• Virus Definitions (Intelligent Updater) December 24, 2005

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: Medium
• Payload: Opens a back door and downloads remote files.

Distribution

• Distribution Level: Medium

TECHNICAL DETAILS

Once executed, Linux.Mare performs the following actions:

1. Opens a back door by connecting to the following servers:
   
   
   • 81.223.104.152
   • 24.224.174.18
     
     
2. Receives commands from the remote attacker to perform the following actions:
   
   
   • Update the worm
   • Execute files
   • Terminate the worm
     
     
3. Downloads and executes the following executable file from the servers listed in Step 1 above:
   
   listen
   
   
4. Downloads the following file, which is an updated version of the executable file referred to in Step 3 above, if this file already exists on the compromised computer:
   
   update.listen
   
   
5. Logs its activities to the following file:
   
   listen.log
   
   Note: The location of this file, and those files referred to in Steps 3 and 4 above, 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.
   
   
6. Scans for vulnerable computers, and attempts to exploit the PHP-Nuke "phpbb_root_path" Arbitrary File Inclusion vulnerability. If successful, a copy of the worm will be downloaded from the following location and executed on the newly compromised computer:
   
   [http://]209.136.48.69/[REMOVED]/cvac

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.