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Discovered: March 22, 2005
Updated: February 13, 2007 12:35:39 PM
Type: Trojan Horse
Systems Affected: Linux

Backdoor.Livehar is a Linux-based Trojan horse that attempts to open a back door on the compromised computer. The Trojan opens a raw IP socket and sends customized ICMP packets through it. This allows the remote attacker to communicate with the back door without opening any ports.

Antivirus Protection Dates

  • Initial Rapid Release version March 22, 2005
  • Latest Rapid Release version March 22, 2005
  • Initial Daily Certified version March 22, 2005
  • Latest Daily Certified version March 22, 2005
  • Initial Weekly Certified release date March 23, 2005

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

Writeup By: Costin Ionescu

Discovered: March 22, 2005
Updated: February 13, 2007 12:35:39 PM
Type: Trojan Horse
Systems Affected: Linux

Backdoor.Livehar has been reported to arrive as a file named icmpd. When this file is executed it does the following:

  1. Checks to see if it is running with root privileges.

  2. Attempts to allocate a raw socket to do the following:

    • Intercept all IP network traffic
    • Send custom packets

  3. Opens a shell, which communicates with the Trojan.

  4. Monitors incoming IP packets. If it receives a special crafted packet (which contains the text 'livthehacker') then the packet is sent as input for the shell program, allowing the hacker to execute commands on the remote computer.

  5. Sends the output from the shell back to the IP address that the packets were originally sent from, so the hacker will see the result of his commands.


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: Costin Ionescu

Discovered: March 22, 2005
Updated: February 13, 2007 12:35:39 PM
Type: Trojan Horse
Systems Affected: Linux

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. Run a full system scan and delete all the files detected as Backdoor.Livehar.

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

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: 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 daily. 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 latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.

2. To scan for and delete the infected files
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected as infected with Backdoor.Livehar, click Delete.

Writeup By: Costin Ionescu