W32.Opaserv.H.Worm

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Discovered: November 11, 2002
Updated: February 13, 2007 12:00:18 PM
Also Known As: Win32.Opaserv.H [CA], WORM_OPASERV.H [Trend], W32/Opaserv-G [Sophos], W32/Opaserv.worm.k [McAfee]
Type: Worm
Systems Affected: Windows
CVE References: CVE-2000-0979



W32.Opaserv.H.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 a file named Instit.bat. It is compressed using UPX.

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

  • The existence of the files Gustav.sap, Institu.bat, or Institu in the root of drive C. This indicates a local infection (that is, the worm was executed on the local computer).
  • The existence of the institu file in the root of drive C. This may indicate a remote infection (that is, the computer was infected by a remote host).
  • The existence of the value

    instit        C:\WINDOWS\instit.bat
    or 
    GustavVED      <Path\original worm name>

    in the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

NOTE: 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.

NOTE: If you are on a network, or have a full time connection to the Internet such as DSL or Cable modem, you must disconnect the computer from the network and the Internet before attempting to remove this worm. If you have shared files or folders, these must be disabled. When you have finished the removal procedure, if you decide to reenable 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


Antivirus Protection Dates

  • Initial Rapid Release version November 12, 2002
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version November 12, 2002
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date November 13, 2002

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

Writeup By: Yana Liu

Discovered: November 11, 2002
Updated: February 13, 2007 12:00:18 PM
Also Known As: Win32.Opaserv.H [CA], WORM_OPASERV.H [Trend], W32/Opaserv-G [Sophos], W32/Opaserv.worm.k [McAfee]
Type: Worm
Systems Affected: Windows
CVE References: CVE-2000-0979


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

It checks for the value

GustavVED

in the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

If the value exists, the worm deletes the file that the GustavVED value points to.

If the GustavVED value does not exist, then the worm determines whether the value

instit

exists in the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

If the value does not exist, the worm adds the value

instit     C:\WINDOWS\instit.bat

to that registry key.

Next it checks whether it is being run as the file C:\Windows\Instit.bat. If it is not, the worm copies itself as this file name and adds the value

GustavVED    <Path\original worm name>

to the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

After the worm checks the registry values and the location from which it is executing, the worm checks to make sure that only one instance of the worm is running in memory; it does this by creating a mutex that has the name GustavoDist.

The worm registers itself as a process if it is not already executing.

The worm then inventories the network looking for "C:\" shares. For each share that it finds, it copies itself to C:\Windows\Instit.bat.

The worm uses a security vulnerability in Microsoft Windows 95/98/Me. It sends single-character passwords to network shares to get access to Windows 95/98/Me file shares without knowing the entire password assigned to the shares. The affected operating systems include:

  • Microsoft Windows 95
  • Microsoft Windows 98
  • Microsoft Windows 98 Second Edition
  • Microsoft Windows Me

A patch for computers that are running these operating systems can be found at http://www.microsoft.com/technet/security/bulletin/MS00-072.asp.

So that Windows 95/98/Me-based computers will run the worm each time that you start Windows, the worm modifies the [windows] section of the C:\Windows\Win.ini file by adding the line

run=c:\Windows\Brasil.exe,c:\Windows\Brasil.pif,c:\Windows\marco!.scr,
c:\windows\scrsvr.exe,c:\windows\instit.bat

NOTES:
  • The worm modifies C:\Windows\Win.ini before it copies itself as C:\Windows\Marco!.scr. Therefore, Symantec antivirus products will find and delete C:\Windows\Marco!.scr after the system has been altered, but not before the worm modifies the Win.ini file. As a result, when you restart the computer, you may see a message that Marco!.scr cannot be found. To fix this, remove the line that the worm added.
  • The worm is apparently coded to add this line to the Win.ini file:

    run=c:\institu

    However, in actual infections or detections, the worm has added the line
    run=c:\Windows\Brasil.exe,c:\Windows\Brasil.pif,
    c:\Windows\marco!.scr,c:\windows\scrsvr.exe,c:\windows\instit.bat

It also creates the file named C:\Institu, which contains the text

run=c:\Windows\Brasil.exe,c:\Windows\Brasil.pif,c:\Windows\marco!.scr,
c:\windows\scrsvr.exe,c:\windows\instit.bat
    The worm appears to be able to update itself by reading files from a Web site whose URL is hard-coded into the worm. It attempts to download an update named Tavinh.scr.

    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: Yana Liu

    Discovered: November 11, 2002
    Updated: February 13, 2007 12:00:18 PM
    Also Known As: Win32.Opaserv.H [CA], WORM_OPASERV.H [Trend], W32/Opaserv-G [Sophos], W32/Opaserv.worm.k [McAfee]
    Type: Worm
    Systems Affected: Windows
    CVE References: CVE-2000-0979



    IMPORTANT - READ THIS FIRST:

      • This worm uses a security vulnerability in Microsoft Windows 95/98/Me. It sends single-character passwords to network shares to get access to Windows 95/98/Me file shares without knowing the entire password that is assigned to the shares. The affected systems include Windows 95, 98, and Me.

        A patch for computers that run these operating systems can be found at http://www.microsoft.com/technet/security/bulletin/MS00-072.asp. If you have not already done so, you must obtain and install the patch to prevent future infections.
      • If you are on a network, or if you have a full time connection to the Internet (such as DSL or cable modem), you must disconnect the computer from the network and the Internet. Disable sharing before you reconnect 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 reinfect the computer after it has been removed, you must remove all shares, clean all computers on the network, patch all systems, and update definitions on all computers before you reconnect to the network or re-enable shares. For instructions on how to do this, see your Windows documentation or the document How to configure shared Windows folders for maximum network protection.
      • If you are removing an infection on a network, first make sure any shares are disabled.


    Removal using the W32.Opaserv.Worm Removal Tool
    This is the easiest way to remove this threat. Symantec Security Response has created a W32.Opaserv.Worm Removal Tool . Click here to obtain the tool. This removal tool can removal all discovered variants of W32.Opaserv.Worm.
     
    Manual Removal
    As an alternative to using the removal tool, you can remove this threat manually. Here are the major steps:
    1. Disconnect from the network.
    2. Update the virus definitions.
    3. Run a full system scan, and delete all files that are detected as W32.Opaserv.H.Worm.
    4. If found, delete the values

      instit        C:\WINDOWS\instit.bat
      GustavVED     <Path\original worm name>

      from the registry key

      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    5. (Windows 95/98/Me only ) Delete the line

      run=c:\Windows\Brasil.exe,c:\Windows\Brasil.pif,
      c:\Windows\marco!.scr,c:\windows\scrsvr.exe,c:\windows\instit.bat

      or

      run=c:\institu

      from C:\Windows\Win.ini.
    For details on how to do this, read the following instructions.

    To disconnect from the network:
    If you are on a network, or if you have a full time connection to the Internet (such as DSL or cable modem), you must 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 reinfect the computer after it has been removed, you must remove all shares, clean all computers on the network, patch all systems, and update definitions on all computers before you reconnect to the network or re-enable shares.For instructions on how to do this, 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 reenable 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


    To update the virus definitions:
    All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:
    • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
    • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.

      Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

    To scan for and delete the infected files:
    1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
    2. Run a full system scan.
    3. If any files are detected as infected with W32.Opaserv.H.Worm, click Delete.

    To remove the value that the worm added to the registry:

    CAUTION : Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
    1. Click Start, and click Run. The Run dialog box appears.
    2. Type regedit and 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 these value:

      instit C:\WINDOWS\instit.bat
      GustavVED <Path\original worm name>
    5. Exit the Registry Editor.

    To delete the line that the worm added to the Win.ini file:
    This is necessary only on Windows 95/98/Me-based computers.

    NOTE: (For Windows Me users only) Due to the file-protection process in Windows Me, a backup copy of the file that you are about to edit exists in the C:\Windows\Recent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this using Windows Explorer, go to C:\Windows\Recent, and in the right pane select the Win.ini file and delete it. It will be regenerated as a copy of the file that you are about to edit when you save your changes to that file.
    1. Click Start, and click Run.
    2. 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.
    3. In the [windows] section of the file, look for an entry similar to the following:

      run=c:\Windows\Brasil.exe,c:\Windows\Brasil.pif,
      c:\Windows\marco!.scr,c:\windows\scrsvr.exe,c:\windows\instit.bat run=c:\institu
    4. Select the entire line. Be sure that you have not selected any other text in the file, and then press Delete.
    5. Click File, and click Save.
    6. Click File, and click Exit.


    Writeup By: Yana Liu