Threat Explorer

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26 September 2007
27 September 2007
Infection Length:
10,752 bytes
Systems Affected:
Linux, Mac, Solaris, Windows
MSIL.Yakizake is a mass-mailing worm that runs within the .NET or Mono framework and requires that Thunderbird is installed.

Antivirus Protection Dates

  • Initial Rapid Release version 26 September 2007 revision 036
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 27 September 2007 revision 002
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date 03 October 2007
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.
Once executed, the worm sends messages with different subject and bodies, depending on the domain suffix in the recipient address, and the presence or absence of particular software on the compromised computer.

The worm sends a copy of itself as an attachment to German email messages with the following characteristics if /gcc can be found in the %path% on Unix systems or Visual Studio can be found in the %path% on Windows systems:

Subject: Programmierung
Ich habe beim Schreiben dieses Programms einen neuen Ansatz verfolgt. Sag mir bitte was du davon hälts.

Attachment: akikaze.exe

Otherwise, the worm sends a copy of itself as an attachment to German email messages with the following characteristics:
Subject: Programmierung
ich habe neulich angefangen zu programmieren!
Das hier ist eines meiner ersten Programme. Was hältst du davon?

Attachment: akikaze.exe

Note: On non-Windows systems, both German message bodies will contain the following text:
Wenn diese Programm sich auf deinem Nicht-Windows-System nich direkt ausführen lassen sollte musst du es wahrscheinlich durch Mono ausführen! (

Messages sent to countries outside of Germany will be in English.

The worm sends a copy of itself as an attachment to English email messages with the following characteristics if /gcc can be found in the %path% on Unix systems or Visual Studio can be found in the %path% on Windows systems:
Subject: Programming
I wrote this program using a new approach. Please tell me what you think of it.

Attachment: akikaze.exe

Otherwise, the worm sends a copy of itself as an attachment to English email messages with the following characteristics:
Subject: Programming
I have recently started to try out programming!
This is one of my first programms. What do you think of it?

Attachment: akikaze.exe

Note: On non-Windows systems, both English message bodies will contain the following text:
If the programm should not work instantly on your non-windows-system you probably need to execute it using mono. (

The worm sends email to every address in the Thunderbird address book.


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.
For Windows:
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.

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.

For Linux and Solaris:
If your Symantec antivirus product detects this threat, delete the files in question.

Once the threat attacks a computer, it is difficult to determine what else the computer has been exposed to. In most cases, changes other than those made by the threat will not have occurred. However, the author of the threat may have been able to use the threat to access the computer to make changes to it. Unless you can be absolutely sure that malicious activity has not been performed on the computer, we recommend completely reinstalling the operating system.

Writeup By: Peter Ferrie