New variant Opaserv

Discussion in 'malware problems & news' started by Pieter_Arntz, Nov 13, 2002.

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  1. Pieter_Arntz

    Pieter_Arntz Spyware Veteran

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    http://vil.mcafee.com/dispVirus.asp?virus_k=99729

    Makes an entry in win.ini RUN= pointing to INSTIT.BAT

    Regards,

    Pieter
     
  2. Randy_Bell

    Randy_Bell Registered Member

    Joined:
    May 24, 2002
    Posts:
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    Location:
    Santa Clara, CA
    Symantec Security Response - W32.Opaserv.H.Worm

    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\Current Version\Run

    NOTE: When the worm runs on Windows 95/98/Millenium-based computers, the worm can spread to other Windows 95/98/Millenium/2000/NT/XP-based computers through open network shares, but the worm cannot run on Windows 2000/NT/XP.

    Type: Worm
    Infection Length: 21,504 bytes
    Systems Affected: Windows 95, Windows 98, Windows NT, Windows 2000, Windows XP, Windows Me
    Systems Not Affected: Macintosh, OS/2, Unix, Linux

    technical details

    When W32.Opaserv.H.Worm runs on Windows 95/98/Millenium-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/Millenium. It sends single-character passwords to network shares to get access to Windows 95/98/Millenium 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/Millenium-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.

    removal instructions

    IMPORTANT - READ THIS FIRST:

    • This worm uses a security vulnerability in Microsoft Windows 95/98/Millenium. It sends single-character passwords to network shares to get access to Windows 95/98/Millenium 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.

    Here are the general removal 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/Millenium 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.

    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/Millenium-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.
     
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