W32.Opaserv.G.Worm http://securityresponse.symantec.com/avcenter/venc/data/w32.opaserv.g.worm.html W32.Opaserv.G.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 the file Marco!.scr. It is compressed using PECompact. This worm attempts to download updates from www.gwmnet.com.br, although the site may already have been shut down. Indicators of infection include: -- The existence of the files Mane!!.dat, FDP!!!!.dat, or Gay.ini 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 Gay.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 registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Current Version\Run contains the string value cronos or Cuzao!Old, which is set to C:\WINDOWS\marco!.scr. NOTES: -- When the worm runs on Windows 95/98/Milennium-based computers, the worm can spread to other Windows 95/98/Milennium/2000/NT/XP-based computers through open network shares, but the worm cannot run on Windows 2000/NT/XP. -- Definitions dated prior to October 30, 2002, may detect this threat as W32.Opaserv.Worm. Also Known As: W32.Opaserv.Worm, WORM_OPASERV.G [Trend], W32/Opaserv-F [Sophos], Win32.Opaserv.G [CA], W32/Opaserv.worm [McAfee] technical details When W32.Opaserv.G.Worm runs on Windows 95/98/Milennium-based computers, it does the following: It checks for the value Cuzao!Old in the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run If the value exists, the worm deletes the file that the Cuzao!Old value points to. If the Cuzao!Old value does not exist, then the worm determines whether the value cronos exists in the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run If the value does not exist, the worm adds the value cronos C:\WINDOWS\marco!.scr to that registry key. Next it checks whether it is being run as the file C:\WINDOWS\marco!.scr. If it is not, it copies itself as this file name and adds the value Cuzao!Old to the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run After the worm checks the registry values and the location from which the worm 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 with the name marquinhos!. 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\Marco!.scr. The worm uses a security vulnerability in Microsoft Windows 95/98/Milennium. It sends single-character passwords to network shares to get access to Windows 95/98/Milennium file shares without knowing the entire password assigned to the shares. The affected systems include, -- Microsoft Windows 95 -- Microsoft Windows 98 -- Microsoft Windows 98 Second Edition -- Microsoft Windows Milennium 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/Milennium-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 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 Win.ini: run= c:\gay.ini 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 It also creates the file named C:\Gay.ini, which contains the text run= c:\Windows\Brasil.exe,c:\Windows\Brasil.pif,c:\Windows\marco!.scr The worm also appears to be able to update itself by reading files from a Web site whose URL is hardcoded within the worm. It also attempts to download an update named Vaisef.exe. removal instructions IMPORTANT - READ THIS FIRST: -- This worm uses a security vulnerability in Microsoft Windows 95/98/Milennium. It sends single character passwords to network shares to get access to Windows 95/98/Milennium file shares without knowing the entire password assigned to the shares. The affected systems include Windows 95, 98, and Milennium. -- 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, you must obtain and install the patch to prevent future infections. -- 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. Disable or password protect file sharing--or set shared files to Read-Only--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, Symantec suggests sharing with read-only access or using password protection. For instructions on how to do this, see your Windows documentation or the document "How to configure shared Windows folders for maximum network protection": http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2000091415173339. -- If you are removing an infection on a network, first make sure any shares are disabled Removal using the W32.Opaserv.G.Worm Removal Tool This is the easiest way to remove this threat. Symantec Security Response has created a W32.Opaserv.Worm Removal Tool: http://securityresponse.symantec.com/avcenter/venc/data/w32.opaserv.worm.removal. This removal tool can remove 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 if connected. 2. Update the virus definitions. 3. Run a full system scan, and delete all files that are detected as W32.Opaserv.G.Worm 4. Delete the values cronos C:\WINDOWS\marco!.scr Cuzao!Old from the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run 5. (Windows 95/98/Milennium only ) Delete the line run=c:\Windows\Brasil.exe,c:\Windows\Brasil.pif,c:\Windows\marco!.scr or run=c:\gay.ini from the 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: http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/199762382617. 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: cronos C:\WINDOWS\marco!.scr Cuzao!Old 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/Milennium-based computers. NOTE: (For Windows Milennium users only) Due to the file-protection process in Windows Milennium, 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 either (or both) of the following: run=c:\Windows\Brasil.exe,c:\Windows\Brasil.pif,c:\Windows\marco!.scr run=c:\gay.ini 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. NOTE: There have been several reports of infections by this worm in which the worm itself was infected with a virus that then also spread to the infected computer. For this reason, we suggest that after you have finished removing W32.Opaserv.G.Worm, that you run a full system scan. If any files are detected as infected with a different threat, go to http://securityresponse.symantec.com/avcenter/vinfodb.html, enter the name of the detection in the field, and then click search. Open the document if one is found and follow any removal instructions.