W32.Opaserv.AE.Worm

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Discovered: January 07, 2004
Updated: February 13, 2007 12:15:51 PM
Type: Worm
Systems Affected: Windows



W32.Opaserv.AE.Worm is a variant of W32.Opaserv.Worm . It is a network-aware worm that spreads across open network shares. It copies itself to the remote computer as the file Natal.scr. The worm is packed with PEPACK.

This worm attempts to download updates from www.4ws.com.br, although the site may have already been shut down. Indicators of infection include:

  • The existence of the files, Putz!!!, Troxxx, Troxxx.dat, or Trossss.gay in %Windir%. This indicates a local infection (that is, the worm was executed on the local computer).
  • The existence of the file lammer! in the root of drive C. This may indicate a remote infection (that is, a remote host infected the computer).
  • The registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run contains the string value Natal or Natal!Old, which is set to %Windir%\Natal.scr.


Notes:
  • When the worm runs on Windows 95/98/Me-based computers, the worm can spread to other Windows 95/98/Me/2000/NT/XP-based computers through open network shares, but the worm cannot run on Windows 2000/NT/XP.
  • If you are on a network, or have a full-time connection to the Internet, such as DSL or Cable modem, disconnect the computer from the network and the Internet before attempting to remove this worm. If you have shared files or folders, disable them. When you have finished the removal procedure, if you decide to re-enable file sharing, Symantec suggests that you do not share the root of drive C. Share specific folders instead. These shares must be password-protected with a secure password. Do not use a blank password.

    Also, before doing so, if you are using Windows 95/98/Me, download and install the Microsoft patch from:

    http://www.microsoft.com/technet/security/bulletin/MS00-072.asp
  • Virus definitions dated January 8, 2004 detect this as W32.Opaserv.Worm.



Antivirus Protection Dates

  • Initial Rapid Release version January 08, 2004
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version January 08, 2004
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date January 14, 2004

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

Writeup By: Fergal Ladley

Discovered: January 07, 2004
Updated: February 13, 2007 12:15:51 PM
Type: Worm
Systems Affected: Windows


When W32.Opaserv.AE.Worm runs on Windows 95/98/Me-based computers, it does the following:

  1. Attempts to create a mutex named 4wsDosFDPS! and exits if the mutex already exists. This ensures that only one instance of the worm is running on the computer.

  2. Registers itself as a service process.

  3. Lowers its priority so that it runs only when the system is otherwise idle.

  4. Copies itself as %Windir%\Natal.scr.


    Note: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows on Windows 95/98/Me) and copies itself to that location.

  5. Checks for the value:

    Natal!Old

    in the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  6. If the value exists, the worm deletes the file to which the Natal!Old value points.

  7. If the Natal!Old value does not exist, then the worm will determine whether the value:

    Natal

    exists in the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  8. If the value does not exist, the worm will add the value:

    "Natal"="%Windir%\Natal.scr"

    to that registry key.

  9. Creates the file named C:\lammer!, which contains the text:

    run=c:\windows\natal.scr

  10. Attempts to contact a predetermined Web site, probably to update itself. The Web site was inactive at the time of this writing.

  11. Uses a security vulnerability in Microsoft Windows 95/98/Me to spread to other computers. The worm sends single-character passwords to network shares, attempting to get access to other Windows 95/98/Me file shares without knowing the entire password. The affected systems include:
    • Microsoft Windows 95
    • Microsoft Windows 98
    • Microsoft Windows 98 Second Edition
    • Microsoft Windows Me


      Note: A patch for computers that are running these operating systems can be found in the Microsoft Security Bulletin MS00-072.

  12. Attempts to copy itself as Natal.scr to vulnerable network shares.

  13. Modifies the[windows]section of the %Windir%\Win.ini file by adding one of the following lines:
    • run= c:\windows\natal.scr
    • run= c:\lammer!

      so that Windows 95/98/Me-based computers will run the worm each time you start Windows.


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: Fergal Ladley

Discovered: January 07, 2004
Updated: February 13, 2007 12:15:51 PM
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. Update the virus definitions.
  2. Disconnect from the network, if connected.
  3. Disable System Restore (Windows Me/XP).
  4. Restart the computer in Safe mode or VGA mode.
  5. Run a full system scan and delete all the files detected as W32.Opaserv.AE.Worm.
  6. Delete the value that was added to the registry.
  7. Edit the Win.ini file.
For specific details on each of these steps, read the following instructions.

1. Updating 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 on U.S. business days (Monday through Friday). 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.

2. Disconnecting from the network
If you are on a network, or have a full-time connection to the Internet, such as DSL or Cable modem, disconnect the computer from the network and the Internet. Disable sharing before reconnecting computers to the network or to the Internet. Because this worm spreads by using shared folders on networked computers, to ensure that the worm does not re-infect the computer after it has been removed, remove all the shares, clean all the computers on the network, patch all the systems, and update the definitions on all the computers before you reconnect to the network or re-enable shares.

For instructions, see your Windows documentation, or the document, "How to configure shared Windows folders for maximum network protection ."


IMPORTANT:
  • Do not skip this step. You must disconnect from the network before attempting to remove this worm.
  • For additional information on file sharing, read your Windows documentation or the document How to configure shared Windows folders for maximum network protection.
  • When you have finished the removal procedure, if you decide to re-enable file sharing, Symantec suggests that you do not share the root of drive C. Share specific folders instead. These shares must be password-protected with a secure password. Do not use a blank password.

    Also, before doing so, if you are using Windows 95/98/Me, you must download and install the Microsoft patch from:

    http://www.microsoft.com/technet/security/bulletin/MS00-072.asp


3. Disabling 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.

4. Restarting the computer in Safe mode or VGA mode
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
  • For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
  • For Windows NT 4 users, restart the computer in VGA mode.

5. Scanning for and deleting 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.Opaserv.AE.Worm, click Delete.

6. Deleting the value from the registry


WARNING: 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 keys only. Read the document, "How to make a backup of the Windows registry ," for instructions.
  1. Click Start, and then click Run. (The Run dialog box appears.)
  2. Type regedit

    Then click OK. (The Registry Editor opens.)

  3. Navigate to the key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

  4. In the right pane, delete the values:
    • Natal
    • Natal!Old

  5. Exit the Registry Editor.

7. Editing the Win.ini file
If you are running Windows 95/98/Me, follow these steps:
  1. The function you perform depends on your operating system:
    • Windows 95/98: Go to step B.
    • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Win.ini file that you need to edit. If this backup copy exists, it will be in the C:\Windows\Recent folder. Symantec recommends that you delete this file before continuing with the steps in this section. To do this:
      1. Start Windows Explorer.
      2. Browse to and select the C:\Windows\Recent folder.
      3. In the right pane, select the Win.ini file and delete it. The Win.ini file will be regenerated when you save your changes to it in step F.

  2. Click Start, and then click Run.
  3. Type the following, and then click OK.

    edit c:\windows\win.ini

    (The MS-DOS Editor opens.)


    Note: If Windows is installed in a different location, make the appropriate path substitution.

  4. In the [windows] section of the file, look for a line similar to:

    run=c:\Windows\Natal.scr

    or:

    run=c:\lammer!

  5. If this line exists, delete everything to the right of "run=".

    When you are done, it should look like:

    run=

  6. Click File, and then click Save.
  7. Click File, and then click Exit.


Note: There have been several reports of infections by this worm in which the worm itself was infected with a virus, which then also spread to the infected computer. For this reason, we suggest that after you have finished removing W32.Opaserv.AE.Worm, that you run a full system scan. If any files are detected as infected with a different threat, go to http://securityresponse.symantec.com/avcenter/vinfodb.html , enter the name of the detection in the field, and then click search. Open the document, if one is found, and follow any removal instructions.


Writeup By: Fergal Ladley