W32.Opaserv.J.Worm

Symantec Security Response - W32.Opaserv.J.Worm

The W32.Opaserv.J.Worm is a variant of the W32.Opaserv.Worm. It is a network-aware worm that spreads across open network shares. This worm copies itself to the remote computer as a file named Srv32.exe. It is compressed using ASPack. The W32.Opaserv.J.Worm also has Backdoor capabilities.

Indicators of the infection include the existence of:

• The files SrvTsk and SrvRes 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 temp.ini 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
  
  Srv32 C:\WINDOWS\Srv32.exe
  or
  Srv32Old <Path\original worm name>
  
  in the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

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.

If you are on a network, or have a full-time connection to the Internet, such as a 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, 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. Instead, share specific folders. These shared folders 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/Millenium, download and install the Microsoft patch from

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

Type: Worm
Infection Length: 18,432 bytes
Systems Affected: Windows 95, Windows 98, Windows NT, Windows 2000, Windows XP, Windows Me
Systems Not Affected: Macintosh, OS/2, UNIX, Linux
CVE References: CVE-2000-0979

technical details

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

It checks for the value

Srv32Old

in the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

If the value exists, the worm deletes the file to which the Srv32Old value points.

If the the Srv32Old value does not exist, then the worm determines whether the value

Srv32

exists in the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

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

Srv32 C:\WINDOWS\Srv32.exe

to that registry key.

Next, the worm checks whether it is being run as the file C:\Windows\Srv32.exe. If it is not, the worm copies itself as this file name and adds the value

Srv32Old <Path\original worm name>

to the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

After the worm checks the registry values and the location from where 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 Srv3231415.

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

Then, the worm takes inventory of the network looking for "C:\" shares. For each share that it finds, it copies itself to C:\Windows\svr32.exe.

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 run these operating systems can be found at http://www.microsoft.com/technet/security/bulletin/MS00-072.asp.

The worm is apparently coded to add the following line to the Win.ini file:

run=c:\windows\src32.exe

However, in actual infections or detections, the worm does not add this line to the file Win.ini.

The worm appears to be able to update itself by reading files from a Web site whose URL is hard-coded into the worm. The worm attempts to download an update named Sccss.

The W32.Opaserv.J.Worm also has Backdoor capabilities, which give an attacker unauthorized access to a compromised computer. The worm opens a randomly chosen TCP port and UDP port to connect to the attacker.

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 assigned to the shares. The affected systems include Windows 95, 98, and Me.
  
  A patch for computers running these operating systems can be found at http://www.microsoft.com/technet/security/bulletin/MS00-072.asp. If you have not already done so, 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, 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 re-infect the computer after it has been removed, remove all he tshares, 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 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.
  
  NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
  
  • 
    1. Disconnect from the network.
    2. Update the virus definitions.
    3. Restart the machine in Safe mode.
    4. Run a full system scan and delete all the files detected as W32.Opaserv.J.Worm.
    5. If any files are found, delete the values
    
    Srv32 C:\WINDOWS\Srv32.exe
    Srv32Old <Path\original worm name>
    
    from the registry key
    
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    
    6. For Windows 95/98/Millenium only, delete the line
    
    run=c:\Windows\Srv32.exe
    
    from C:\Windows\Win.ini, if this line exists.
  
  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 specified keys. 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, and then click OK. The Registry Editor opens.
    3. Navigate to the key
    
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    
    4. In the right pane, delete these value:
    
    Srv32 C:\WINDOWS\Srv32.exe
    Srv32Old <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 you are 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 you are to edit when you save your changes to that particular file.
  
  • 
    1. Click Start, and then 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
    
    run=C:\WINDOWS\Srv32.exe
    
    4. Select the entire line. Be sure that you have not selected any other text in the file. Then press Delete.
    5. Click File, then click Save.
    6. Click File, then click Exit.