Discovered: December 24, 2002
Updated: February 13, 2007 11:41:59 AM
Also Known As: W32/Opaserv.worm.m [McAfee], W32/Opaserv.worm.n [McAfee], W32/Opaserv-H [Sophos], W32/Opaserv-I [Sophos], W32/Opaserv-L [Panda], Opaserv.F [F-Prot], WORM_OPASERV.M [Trend]
Systems Affected: Windows
CVE References: CVE-2000-0979
W32.Opaserv.K.Worm is a network-aware worm that spreads across open network shares. This worm copies itself to the remote computer as a file named Mqbkup.exe. It is compressed with a PECompact packer.
Before you follow the steps in this document, if you are running Windows 95/98/Me, download and install the Microsoft patch from: http://www.microsoft.com/technet/security/bulletin/MS00-072.asp .
NOTE: Some of W32.Opaserv.K.Worm functionality is specific to the Windows 95/98/Me systems, while some of it is only functional on Windows NT/2000/XP.
If you are on a network or have a full-time connection to the Internet, such as a DSL or cable modem, disconnect the computer from the network and the Internet before attempting to remove this worm. If you have shared the 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 the specific folders. These shared folders must be password-protected with a secure password. Do not use a blank password.
Recently, a new variant of the W32.Opaserv.K.Worm was discovered. The differences between this new variant and the old one are:
- File name is Mmstask.exe, instead of Mqbkup.exe.
- Registry key that the new variant adds is Mstask or Mstasksys.
- File size is 20,480 bytes.
Symantec antivirus products have already detected this new variant as W32.Opaserv.K.Worm.
Antivirus Protection Dates
- Initial Rapid Release version December 24, 2002
- Latest Rapid Release version August 08, 2016 revision 023
- Initial Daily Certified version December 24, 2002
- Latest Daily Certified version August 09, 2016 revision 001
- Initial Weekly Certified release date December 24, 2002
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.
The W32.Opaserv.K.Worm is a variant of the W32.Opaserv.Worm . When the W32.Opaserv.K.Worm runs, it performs the following actions:
- 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:
- 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:
- 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:
- 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:
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:
If you are outside the USA, please look up the correct contact information
on our website, at:
Business Software Alliance
Promoting a safe & legal online world.
- First, the worm creates the following files:
- If all the conditions for the payload (as described in step 2) were not met, the worm performs the following actions:
- 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.
- 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.
- Creates the "mqbkup61616" mutex. This mutex allows only one instance of the W32.Opaserv.K.Worm to execute in memory.
- Creates the value:
in the registry key:
so that the worm starts when you restart Windows.
- If the operating system is Windows 95/98/Me, the worm registers itself as a service process to continue running after you log off.
- 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:
- 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.
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.
- These removal instructions are useful only if the payload has not run. If the payload has run and you saw the "Illegal Microsoft Windows license detected" message, as described in the previous section, it is possible that your computer is no longer functional.
- If you can no longer start your computer, we suggest that you contact the computer's manufacturer for assistance. You may have to repartition the hard drive, and re-install the operating system. You will also need to restore data from a clean backup.
- This worm uses a security vulnerability in Microsoft Windows 95/98/Me. It sends single-character passwords to network shares to get access to the Windows 95/98/Me file shares, without knowing all the passwords 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, 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 a 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 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, refer to 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 that all the shares are disabled.
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 remove all the discovered variants of W32.Opaserv.Worm through W32.Opaserv.K.Worm.
As an alternative to using the removal tool, you can manually remove this threat as well. These instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
Perform the following steps to remove the W32.Opaserv.K.Worm:
- Disconnect from the network.
- Update the virus definitions.
- Do one of the following:
- Windows 95/98/Me: Restart the computer in Safe mode.
- Windows NT/2000/XP: Stop the process of running the worm.
- Run a full system scan and delete all the files detected as W32.Opaserv.K.Worm.
- Reverse the changes the worm made to the registry.
- For Windows 95/98/Me only, delete the line:
1. Disconnecting from the network
If you are on a network, or if you have a full-time connection to the Internet, such as a 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 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.
- 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."
- If you are running Windows 95/98/Me, download and install the Microsoft patch from http://www.microsoft.com/technet/security/bulletin/MS00-072.asp.
- 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 the specific folders. These shared folders must be password-protected with a secure password. Do not use a blank password.
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 the 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), in the "Protection" section, at the top of this writeup.
- 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), in the "Protection" section, at the top of this writeup.
The 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.
3. Restarting the computer in Safe mode or ending the Trojan process
- Windows 95/98/Me
Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document, "How to start the computer in Safe Mode."
- Windows NT/2000/XP
To end the Trojan process:
- Press Ctrl+Alt+Delete once.
- Click Task Manager.
- Click the Processes tab.
- Double-click the Image Name column header to alphabetically sort the processes.
- Scroll through the list and look for Mqbkup.exe.
- If you find the file, click it, and then click End Process.
- Exit the Task Manager.
4. Scanning for and deleting the infected files
- Start your Symantec antivirus program and make sure that it is configured to scan all the files.
- For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
- For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan All Files."
- Run a full system scan.
- If any files are detected as infected with W32.Opaserv.K.Worm, click Delete.
5. Reversing the changes the worm made 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 the specified keys only. Read document, "How to make a backup of the Windows registry ," for instructions.
- Click Start, and then click Run. (The Run dialog box appears.)
- Type regedit, and then click OK. (The Registry Editor opens.)
- Navigate to the following key:
- In the right pane, delete the following value:
- Exit the Registry Editor.
6. Deleting the line that the worm added to the Win.ini file
This step is necessary on Windows 95/98/Me-based computers only.
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.
- Click Start, and then click Run.
- Type the following:
Then click OK. (The MS-DOS Editor opens.)
NOTE: If Windows is installed in a different location, make the appropriate path substitution.
- In the [windows] section of the file, look for an entry similar to:
- Select the entire line. Be sure that you have not selected any other text in the file. Then press Delete.
- Click File, and then click Save.
- Click File, and then click Exit.
Writeup By: Serghei Sevcenco