W32.Toal.A@mm

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Discovered: October 23, 2001
Updated: February 13, 2007 11:37:30 AM
Also Known As: W32/AntiWar
Type: Worm, Virus


W32.Toal.A@mm is a mass-mailing email worm. The worm arrives as an attachment named Binladen_brasil.exe with a random subject line that makes a reference to the current situation in Afghanistan. The subject can be in a variety of different languages. The message body will be blank.

The worm exploits a vulnerability in Microsoft Outlook and Outlook Express in an attempt to execute itself when you open or even preview the message. Information on this, and a patch for the vulnerability can be found at http://www.microsoft.com/technet/security/bulletin/MS01-020.asp .

The worm creates Invictus.dll, which contains routines to infect executable files on the system and network drives. The worm also creates an open share on drive C.

This worm uses the file Invictus.dll to spread. Invictus.dll is detected by Norton AntiVirus as W32.Invictus.dll. This file is crucial to the propagation of the worm, and the worm may not function properly without it.

Antivirus Protection Dates

  • Initial Rapid Release version October 23, 2001
  • Latest Rapid Release version February 07, 2018 revision 024
  • Initial Daily Certified version October 23, 2001
  • Latest Daily Certified version February 08, 2018 revision 002

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

Writeup By: Andre Post

Discovered: October 23, 2001
Updated: February 13, 2007 11:37:30 AM
Also Known As: W32/AntiWar
Type: Worm, Virus


When the worm is executed, it queries a mutex to see whether another copy of itself is running. If another copy is already running, the worm exits. Otherwise, it creates a mutex and then creates the following files:

  • %System%\Invictus.dll. This file is used to infect executable files on the system.
  • %Windows%\<3 random characters>.exe. The Hidden attribute of this file is turned on, and the file is executed immediately after being created. This file is run-time compressed, and it orchestrates the entire worm execution flow by performing some actions itself and by calling functions in Invictus.dll.

NOTES:
  • %Windows% is a variable. The worm locates the Windows folder (by default this is C:\Windows or C:\Winnt) and creates the file in that location.
  • %System% is a variable. The worm locates the Windows System folder (by default this is C:\Windows\System or C:\Winnt\System32) and creates the file in that location.

Next, the worm modifies the System.ini file. The line

shell=Explorer.exe

is changed to

shell=Explorer.exe [3 random characters].exe

This causes the worm to run the next time that you restart the computer.

The worm then searches for files to infect by using undocumented TaskMan API functions. Infections may be both polymorphic and entry-point obscuring. The worm specifically infects Hh.exe, which is a standard Windows executable file.

The worm also enumerates Network Neighborhood to infect remote machines. The worm copies itself as a random three-letter name with the .exe extension to the remote Windows directory and Invictus.dll to the remote Windows System directory. To execute itself on the remote system, the worm modifies the remote System.ini file, as mentioned previously.

The worm gathers email addresses by searching the ICQ White Pages, which reside on an ICQ Web server. To send itself, the worm uses an educated guess at what is an appropriate email server. For example, if the email address is joeuser@domain.tld, the worm will use the email servers smtp.domain.tld or mail.domain.tld. When it sends the email message, the worm attaches the infected Hh.exe file as Binladen_brasil.exe. The worm does not require a particular email client to propagate.

The message body is blank and the subject will vary. The subject lines are all references to the current situation in Afghanistan and may be in different languages. The language of the subject line is chosen based on the language version of the operating system.

The worm attempts to save cached networking passwords to a local file using an undocumented Windows 95 function. This fails on other versions of Windows.

The worm creates a share on the local drive C drive. It shares drive C by modifying the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Network\LanMan

The worm also attempts to disable antivirus software in memory.

Depending on the length of time that has passed since it was first executed, the worm may display messages using randomly changing background and text colors that refer to the current activity in Afghanistan. Then a message box is displayed, and random rectangles on the screen are interchanged.

Finally, the worm sleeps for five minutes and repeats the infection process.

Norton AntiVirus already detects Invictus.dll as W32.Invictus.dll . This file is crucial to the propagation of the worm, and the worm may not function properly without it.

Recommendations

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: Andre Post

Discovered: October 23, 2001
Updated: February 13, 2007 11:37:30 AM
Also Known As: W32/AntiWar
Type: Worm, Virus


  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Edit the System.ini file, as follows:
    1. Click Start, and click Run.
    2. Type the following, and then click OK:

      edit c:\windows\system.ini

      The MS-DOS Editor opens.

      NOTE: If Windows is installed in a different location, make the appropriate path substitution.
    3. Locate the line that begins with shell=
    4. Position the cursor immediately to the right of the equal sign.
    5. Press Shift+End to select all of the text to the right of the equal sign, and then press Delete.
    6. Type the following text:

      explorer.exe

      The line should now look like:

      shell=explorer.exe

      NOTE: On some computers there may be an entry other than Explorer.exe after shell= . If this is the case and you are running an alternative Windows shell, then change this line to shell=explorer.exe for now. You can change it back to your preferred shell after you have finished this procedure.
    7. Click File, click Exit, and then click Yes when you are prompted to save the changes.
  3. If you are on a network, remove the open share on drive C. See your network administrator for information on how to do this.
  4. Restart the computer.

    NOTE: When the computer restarts, it is likely that infected files will be found. We recommend that you attempt to repair the infected files. Quarantine any file that is not repairable.
  5. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  6. Run a full system scan.


Writeup By: Andre Post