Linux.Backdoor.Rexob

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Discovered: July 26, 2007
Updated: July 27, 2007 5:30:09 PM
Type: Trojan
Infection Length: 637,691 bytes
Systems Affected: Linux

Linux.Backdoor.Rexob is a generic detection for a Trojan horse that opens a back door on the compromised computer.

Antivirus Protection Dates

  • Initial Rapid Release version July 26, 2007 revision 018
  • Latest Rapid Release version August 20, 2008 revision 017
  • Initial Daily Certified version July 26, 2007 revision 017
  • Latest Daily Certified version August 20, 2008 revision 016
  • Initial Weekly Certified release date August 01, 2007

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Elia Florio

Discovered: July 26, 2007
Updated: July 27, 2007 5:30:09 PM
Type: Trojan
Infection Length: 637,691 bytes
Systems Affected: Linux

The Trojan has a server component, which is installed on the compromised computer by some other malware.

When executed, it asks for a password and displays the following message:
*---------
| BOXER Kit 0.99 (BETA3)
| (c) ADN
.

Once the back door server component is installed, it allows the attacker to perform the following actions:

  • Execute commands
  • Execute binary files
  • Hide and unhide process
  • Upload and download files from the compromised computer
  • Steal system information
  • Connect to remote host
  • Restart the computer

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • 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.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a 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.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. 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.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Elia Florio

Discovered: July 26, 2007
Updated: July 27, 2007 5:30:09 PM
Type: Trojan
Infection Length: 637,691 bytes
Systems Affected: Linux

The following instructions pertain to Symantec AntiVirus for Linux.

  1. Update the virus definitions.
  2. Run a full system scan.

1. 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. For Symantec AntiVirus for Linux, LiveUpdate definitions are updated daily.
  • Downloading the definitions using Intelligent Updater. The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them.

2. To run a full system scan

To run a full system scan in Linux, open a command line and type the following:

sav manualscan --scan /

If any files are detected, follow the instructions displayed by your antivirus program.

Writeup By: Elia Florio