W32.Opaserv.K.Worm

1. Searches the Win.ini file for the [msappfont] section. If the worm:
   • Finds the section (which is not normally part of this file), it looks at the "value=" line, which is a character followed by ASCII code, indicating the infection day with the value 30 added.
   • Finds the section but cannot retrieve the information in the "valid=" line, it creates this value by adding the current day. The worm also creates the "font=" and "style=" lines within the same section. The worm uses them to track the day of its execution.
   • Does not find the section, it creates the section as:
     
     [msappfont]
     value=[encoded day]
     font=[encoded month]
     style=[encoded day]
     
     
2. If the current date is from December 24 to December 31 of any year, or if the current year is greater than 2002, the worm checks whether at least two days have passed since it last ran. If so, then the worm checks for the presence of a local file, named C:\Win.ini. (A legitimate Windows file of the same name normally resides in the C:\Windows folder.) The presence of this file indicates that an infection occurred across a network. If the worm finds this file, it triggers the following payload:
   1. First, the worm creates the following files:
      • C:\Msdos.sys (19 bytes): This file contains an option not to display the Windows logo image at startup.
      • C:\Autoexec.bat (15 bytes): This file contains an instruction to run Mslicenf.com.
      • C:\Mslicenf.com (1,706 bytes): When this file runs, it overwrites the MBR of all the physical drives with itself. The code contained in Mslicenf.com destroys all the data on all the physical drives and displays a message.
      • C:\Boot.ini (88 bytes): If the operating system is Windows NT/2000/XP, this file causes the operating system to load and run C:\Bootsect.dos.
      • C:\Bootsect.dos (512 bytes).
      • If the operating system is Windows NT/2000/XP, this file will be loaded and run. The code contained in Bootsect.dos will destroy all the data on all the physical drives.
      • C:\Boot.exe (4096 bytes): When this file runs, it shuts down the system and restarts it. The system is restarted by forcing processes to end (any opened documents are closed without having their contents saved). This file is not malicious.
      • Under Windows Me, the worm enables the real DOS mode by patching the following files:
        • C:\IO.sys
        • C:\Command.com
        • C:\Windows\System\Regenv32.exe
   2. Then, the worm runs C:\Boot.exe to reboot the system, at which point, the payload runs:
      • Under Windows NT/2000/XP; the code contained in Bootsect.dos will destroy all the data on all the physical drives.
      • Under Windows 95/98/Me; the file C:\Mslicenf.com is executed in DOS mode (the system files of Windows Me are patched to provide the DOS mode). When C:\Mslicenf.com is run, it will overwrite every MBR of every physical and floppy disk drive with itself.
      • Under Windows 95/98/Me, the system reboot will activate the code of the compromised MBR, which performs the following actions:
        • It disables the keyboard input.
        • It reads the Seconds field from CMOS and uses that value as a key to fill a table with 63 pseudo-random numbers.
        • It then uses this particular table to address in CHS-format the sector locations, which are overwritten with the pseudo-random table itself.
        • Such data destruction is repeated for every partition of every physical drive. This results in an enormous amount of data loss. A particular sector of the physical drives is then marked to identify that the payload was performed on it.
        • Then, the code displays this message:
          
          NOTICE:
          
          Illegal Microsoft Windows license detected!
          You are in violation of the Digital Millennium Copyright Act!
          
          Your unauthorized license has been revoked.
          
          For more information, please call us at:
          
          1-888-NOPIRACY
          If you are outside the USA, please look up the correct contact information
          on our website, at:
          
          www.bsa.org
          
          Business Software Alliance
          Promoting a safe & legal online world.
          
          
3. If all the conditions for the payload (as described in step 2) were not met, the worm performs the following actions:
   1. Depending on the variant, if the original file name of the worm is not %windir%\Mqbkup.exe or %windir%\Mmstask.exe, it copies itself as %windir%\Mqbkup.exe or %windir%\Mmstask.exe, and then deletes itself from the original location.
   2. Then, the worm updates the registry and quits, ensuring that it runs at the next system startup as Mqbkup.exe or Mmstask.exe.
      
      NOTE: %Windir% is a variable. The worm locates the Windows main installation folder (by default, this is C:\Windows or C:\Winnt) and uses it as a destination folder.
      
   3. Creates the "mqbkup61616" mutex. This mutex allows only one instance of the W32.Opaserv.K.Worm to execute in memory.
   4. Creates the value:
      
      mqbkup    %windir%\mqbkup.exe
      
      or:
      
      mqbkupdbs    %windir%\mqbkup.exe
      
      or:
      
      mstask    %windir%\mstask
      
      or:
      
      mstasksys    %windir%\mstasksys
      
      in the registry key:
      
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
      
      so that the worm starts when you restart Windows.
      
   5. If the operating system is Windows 95/98/Me, the worm registers itself as a service process to continue running after you log off.
   6. Takes an inventory of the network, looking for "C:\" shares. For each share the worm finds, it attempts to perform these actions:
      • Copy itself to C:\Windows\Mqbkup.exe.
      • Add the following line to the Win.ini file on the infected network computer:
        
        run=c:\windows\mqbkup.exe
        
   7. To replicate across the network, the worm uses a security vulnerability in Microsoft Windows 95/98/Me. The worm sends single-character passwords to network shares to obtain access to the Windows 95/98/Me file shares, without knowing all the passwords 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 is available at http://www.microsoft.com/technet/security/bulletin/MS00-072.asp.

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.