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Discovered: December 10, 2013
Updated: December 12, 2013 10:55:26 AM
Type: Worm
Infection Length: Varies
Systems Affected: Linux

Linux.Aidra is a worm that may open a back door on the compromised computer, may perform DoS attacks, and spreads through IRC.

Antivirus Protection Dates

  • Initial Rapid Release version December 10, 2013 revision 034
  • Latest Rapid Release version September 09, 2016 revision 009
  • Initial Daily Certified version December 11, 2013 revision 001
  • Latest Daily Certified version September 10, 2016 revision 001
  • Initial Weekly Certified release date December 11, 2013

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

Writeup By: Kaoru Hayashi

Discovered: December 10, 2013
Updated: December 12, 2013 10:55:26 AM
Type: Worm
Infection Length: Varies
Systems Affected: Linux

When the worm is executed, it saves its process ID to the following file:

The worm then attempts to connect to the following IRC server on TCP port 6667:

Note: The worm waits for commands from the attacker.

The worm may attempt to connect to TCP port 23 at one of the following locations:

  • Specific attacker-defined IP address
  • Range-based IP address of compromised system (if the a.b.c.d is compromised address, worm scans a.b.0.0 - a.b.255.255)
  • Randomly generated IP addresses (x.y.0.0 - x.y.255.255, x and y are randomly generated)

The worm may use attacker-supplied IDs and passwords.

The worm may attempt to download a shell script from the following location:

Note: The shell script may download and execute additional malicious files (detected as Linux.Aidra).

The worm may also receive a command from the IRC server to perform denial of service (DoS) attacks.


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: Kaoru Hayashi

Discovered: December 10, 2013
Updated: December 12, 2013 10:55:26 AM
Type: Worm
Infection Length: Varies
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: Kaoru Hayashi