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Discovered: November 10, 2005
Updated: November 10, 2005 11:01:57 PM
Infection Length: 10,240 bytes
Systems Affected: Windows

Backdoor.Ryknos is a Trojan horse with back door capabilities.

Technical Description

Backdoor.Ryknos is a Trojan horse with back door capabilities.

Analysis revealed that W32.Looksky.B (MCID 6121) and Backdoor.Ryknos are similar in construction with the major difference appearing to be the exploitation of SecurityRisk.First4DRM by Backdoor.Ryknos.

Once executed, the Trojan copies itself as the following file:

The Trojan will not be installed if the compromised computer has the XCP software present, which is itself installed when inserting some Sony BMG content-protected music CDs.

However, if the XCP software is installed after the Trojan, then this software will hide the copy of the Trojan file and the registry subkey it creates.

The Trojan then creates one of the following mutexes, so that only one instance of it runs on a compromised computer at any one time:

Next, the Trojan creates the following registry entry:
HKEY_CURRENT_USER\WkbpsevaXImgvkwkbpXSmj`kswXGqvvajpRavwmkjXVqj\"$sys$drv" = "$sys$drv.exe"

As a result of a code bug, the Trojan will attempt, and fail, to create a registry subkey under the following subkey:

Next, the Trojan attempts to send a notification message to a predetermined IP address, using TCP port 8080.

The Trojan also attempts to add itself as a trusted application to the Windows Firewall.

The Trojan provides back door capabilities by connecting to the IRC channel #sony and listening for commands.

These commands can allow a remote attacker to perform any of the following actions:
Send sensitive information, such as the host and user name, operating system version, and IP address
Download and execute remote files

The Trojan contacts the following Web site and attempts to download a file which has been detected as a W32.Looksky.B (MCID 6121) variant:


Removal using the FixRyknos.exe Removal Tool
Symantec Security Response has developed a removal tool to clean the infections of Backdoor.Ryknos. Use this removal tool first, as it is the easiest way to remove this threat.

Manual Removal:

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan.
  4. Delete any values added to the registry.

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

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).

2. 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.

    If you use Norton AntiVirus 2006, Symantec AntiVirus Corporate Edition 10.0, or newer products, LiveUpdate definitions are updated daily. These products include newer technology.

    If you use Norton AntiVirus 2005, Symantec AntiVirus Corporate Edition 9.0, or earlier products, LiveUpdate definitions are updated weekly. The exception is major outbreaks, when definitions are updated more often.

  • 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.

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 .

3. To run a full system scan
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.

    For Norton AntiVirus consumer products: Read the document: How to configure Norton AntiVirus to scan all files.

    For Symantec AntiVirus Enterprise products: Read the document: How to verify that a Symantec Corporate antivirus product is set to scan all files.

  2. Run a full system scan.
  3. If any files are detected, follow the instructions displayed by your antivirus program.
Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode . Once you have restarted in Safe mode, run the scan again.
After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [FILE PATH]
Message body: Windows cannot find [FILE NAME]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.

4. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. For instructions refer to the document: How to make a backup of the Windows registry .
  1. Click Start > Run.
  2. Type regedit
  3. Click OK.

    Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.

  4. Navigate to and delete the following entry:
    HKEY_CURRENT_USER\WkbpsevaXImgvkwkbpXSmj`kswXGqvvajpRavwmkjXVqj\"$sys$drv" = "$sys$drv.exe"

  5. Exit the Registry Editor.

    Note: If the risk creates or modifies registry subkeys or entries under HKEY_CURRENT_USER, it is possible that it created them for every user on the compromised computer. To ensure that all registry subkeys or entries are removed or restored, log on using each user account and check for any HKEY_CURRENT_USER items listed above.

Writeup By: Elia Florio