W32.Assiral@mm

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Discovered: February 22, 2005
Updated: February 13, 2007 12:34:00 PM
Also Known As: Email-Worm.Win32.Ariss.a [Kasp, W32/Laris.worm [McAfee], W32/Assiral-A [Sophos], WORM_ASSIRAL.A [Trend Micro]
Type: Worm
Systems Affected: Windows


W32.Assiral@mm is a mass-mailing worm that sends a copy of itself to email addresses gathered from a compromised computer. The email has the following characteristics:
Subject: Re: LOV YA!
Attachment: LOVE_LETTER.TXT.exe

Antivirus Protection Dates

  • Initial Rapid Release version February 23, 2005
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version February 23, 2005
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date February 23, 2005

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

Writeup By: Takayoshi Nakayama

Discovered: February 22, 2005
Updated: February 13, 2007 12:34:00 PM
Also Known As: Email-Worm.Win32.Ariss.a [Kasp, W32/Laris.worm [McAfee], W32/Assiral-A [Sophos], WORM_ASSIRAL.A [Trend Micro]
Type: Worm
Systems Affected: Windows


When W32.Assiral@mm is executed, it performs the following actions:

  1. Creates the following files:

    • C:\MESSAGE.txt
    • C:\MS_LARISSA.exe
    • %Windir%\SpoolMgr.exe
    • %Windir%\love_letter.txt.exe
    • %System%\MS_LARISSA.exe
    • C:\WINDOWS\WinVBS_32.vbs
    • C:\WINDOWS\System32\REG_32.vbs
    • C:\LARISSA_ANTI_BROPIA.html

      Notes:
    • %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
    • %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows (Windows 95/98/Me/XP)or C:\Winnt (Windows NT/2000).

  2. Adds the values:

    "MS_LARISSA" = "%System%\MS_LARISSA.exe"
    "spoolsv manager"  = "%Windir%\SpoolMgr.exe"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    so that the worm runs every time Windows starts.

  3. Modifies the value to:

    "Start Page" = "[Web site on the geocities.com domain]"

    in the registry key:

    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Main

    to redirect the Internet Explorer Start page.

  4. Executes the following files:

    • Reg_32.vbs.
    • WinVBS_32.vbs

  5. Adds the values:

    "NoRun" = "1"
    "NoDrives" = "0x3ffffff"

    to the registry subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    \Policies\Explorer

    to disable various Window functions.

  6. Adds the values:

    "DisableRegistryTools" = "1"
    "NoAdminPage" = "1"

    to the registry subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    \Policies\System

    to disable various Window functions.

  7. Adds the value:

    "Disabled" = "1"

    to the registry subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    \Policies\WinOldApp

    to disable various Windows functions.

  8. Adds the values:

    "Contacts" = "[number of contacts in the Microsoft Outlook Address Book]"
    "[sent to each email address]" = "1"

    to the registry subkey:

    HKEY_CURRENT_USER\Software\Microsoft\WAB

  9. May open a browser window and displays the following HTML file:



    Note: The image above has been edited.

  10. Attempts to copy itself to network shares and to the A drive.

  11. Executes C:\WINDOWS\WinVBS_32.vbs and sends a copy of itself to email addresses gathered from the compromised computer.

    The email has the following characteristics:

    Subject: Re: LOV YA!

    Attachment: LOVE_LETTER.TXT.exe

    Message: Kindly read and reply to my LOVE LETTER in the attachments :-)

  12. Opens a browser window and displays the following message, when the attachment is opened:



    Note: The image above has been edited.


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: Takayoshi Nakayama

Discovered: February 22, 2005
Updated: February 13, 2007 12:34:00 PM
Also Known As: Email-Worm.Win32.Ariss.a [Kasp, W32/Laris.worm [McAfee], W32/Assiral-A [Sophos], WORM_ASSIRAL.A [Trend Micro]
Type: Worm
Systems Affected: 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. Do one of the following:
    • Windows 95/98/Me: Restart the computer in Safe mode.
    • Windows NT/2000/XP: End the malicious process.
  4. Run a full system scan and delete all the files detected as W32.Assiral@mm.
  5. Reverse the changes made to the registry.
  6. Reset the Internet Explorer Start page.
  7. Reset the Internet Explorer Search page.
For 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, re-enable 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: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
  • 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. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).

    The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. To restart the computer in Safe mode or end the malicious process
    Windows 95/98/Me
    Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."

    Windows NT/2000/XP
    To end the malicious process:
    1. Press Ctrl+Alt+Delete once.
    2. Click Task Manager.
    3. Click the Processes tab.
    4. Double-click the Image Name column header to alphabetically sort the processes.
    5. Scroll through the list and look for W32.Assiral@mm.
    6. If you find the file, click it, and then click End Process.
    7. Exit the Task Manager.
4. To scan for and delete the infected files
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected as infected with W32.Assiral@mm, click Delete.
  4. If you are still in Safe mode, restart the computer in Normal mode before proceeding to the next section.

5. To reverse the changes made to 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. Read the document, "How to make a backup of the Windows registry ," for instructions.

  1. Click Start > Run.
  2. Type regedit

    Then click OK.

  3. Navigate to the subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

  4. In the right pane, delete the values:

    "MS_LARISSA" = "%System%\MS_LARISSA.exe"
    "spoolsv manager"  = "%Windir%\SpoolMgr.exe"

  5. Navigate to the subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    \Policies\Explorer

  6. In the right pane, delete the values:

    "NoRun" = "1"
    "NoDrives" = "0x3ffffff"

  7. Navigate to the subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    \Policies\System

  8. In the right pane, delete the values:

    "DisableRegistryTools" = "1"
    "NoAdminPage" = "1"

  9. Navigate to the subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    \Policies\WinOldApp

  10. In the right pane, delete the value:

    "Disabled" = "1"

  11. Navigate to the subkey:

    HKEY_CURRENT_USER\Software\Microsoft\WAB

  12. In the right pane, delete the values:

    "Contacts" = "[number of contacts in the Microsoft Outlook Address Book]"
    "[sent to each email address]" = "1"

  13. Exit the Registry Editor.

  14. Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."
6. To reset the Internet Explorer home page
  1. Start Microsoft Internet Explorer.
  2. Connect to the Internet, and then go to the page that you want to set as your home page.
  3. Click Tools > Internet Options.
  4. In the Home page section of the General tab, click Use Current > OK.

For additional information, or if this procedure does not work, read the Microsoft® Knowledge Base article, "Home Page Setting Changes Unexpectedly, or You Cannot Change Your Home Page Setting, Article ID 320159 ."

7. To reset the Internet Explorer Search page
Follow the instructions for your version of Windows.

Windows 98/Me/2000
  1. Start Microsoft Internet Explorer.
  2. Click the Search button on the toolbar.
  3. In the Search pane, click Customize.
  4. Click Reset.
  5. Click Autosearch Settings.
  6. Select a search site from the drop-down list, and then click OK.
  7. Click OK.

Windows XP
Because Windows XP is set by default to use animated characters in the search, how you do this can vary. Read all the instructions before you start.
  1. Start Microsoft Internet Explorer.
  2. Click the Search button on the toolbar.
  3. Do one of the following:
    • If the pane that opens looks similar to this picture:





      click the word Customize. Then skip to step h.

    • If the pane that opens has the words "Search Companion" at the top, and the center looks similar to this picture:





      click the Change preferences link as shown above. Proceed with step d.

  4. Click the Change Internet search behavior link.
  5. Under "Internet Search Behavior," click With Classic Internet Search.
  6. Click OK. Then close Internet Explorer. (Close the program for the change to take effect.)
  7. Start Internet Explorer. When the search pane opens, it should now look similar to this:





    Click the word Customize, and then proceed with the next step.

  8. In the Search pane, click Customize.
  9. Click Reset.
  10. Click Autosearch Settings.
  11. Select a search site from the drop-down list, and then click OK.
  12. Click OK.
  13. Do one of the following:
    • If you were using (or want to continue using) the "Classic Internet Search" panel, stop here (or proceed with the next section).
    • If you want to go back to the "Search Companion" search (it usually has an animated character at the button), proceed with step n.

  14. Click the word Customize again.
  15. In the "Customize Search Settings" window, click Use Search Companion > OK.
  16. Close Internet Explorer. The next time you open it, it will again use the Search Companion.


Writeup By: Takayoshi Nakayama