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Discovered: August 05, 2008
Updated: August 05, 2008 5:24:41 PM
Type: Trojan
Infection Length: 23,984 bytes; 664,296 bytes; 561,032 bytes
Systems Affected: Linux

Linux.Phalax is a Linux Kernel rootkit that installs a back door on the compromised computer.

Antivirus Protection Dates

  • Initial Rapid Release version August 05, 2008 revision 023
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version August 05, 2008 revision 021
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date August 06, 2008

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

Writeup By: Alfredo Pesoli

Discovered: August 05, 2008
Updated: August 05, 2008 5:24:41 PM
Type: Trojan
Infection Length: 23,984 bytes; 664,296 bytes; 561,032 bytes
Systems Affected: Linux

When the rootkit executes, it creates the following folders:

  • /usr/share/.home.ph1/
  • /usr/share/.home.ph1/tty/

It also creates the following files:
  • /usr/share/.home.ph1/cb
  • /etc/host.ph1/hostname
  • /usr/share/.home.ph1/.phalanx
  • /usr/share/.home.ph1/.sniff

Next, the rootkit overwrites the following file with a malicious component, which opens a back door on the compromised computer:

The rootkit hides its presence on the computer by hooking the following OS syscalls:
  • read
  • lstat64
  • lstat
  • getdents64
  • open

It then connects to a remote host, which can be specified by the attacker.

The remote host is chosen by sending a specially crafted request with a passkey from a local or a remote shell, for example:
echo 'phalanx1!111.222.333.444!PORT[PADDING]'

The rootkit enables a remote attacker to execute commands with full system privileges.


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: Alfredo Pesoli

Discovered: August 05, 2008
Updated: August 05, 2008 5:24:41 PM
Type: Trojan
Infection Length: 23,984 bytes; 664,296 bytes; 561,032 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: Alfredo Pesoli