W32.Stator@mm

SUMMARY

W32.Stator@mm is a mass-mailing worm program. It renames specific Windows programs so that they have a file extension of .vxd, and it then uses the original file names for duplicate copies of the worm itself.

Protection

• Virus Definitions (LiveUpdate™ Weekly) April 25, 2001
• Virus Definitions (Intelligent Updater) April 23, 2001

Threat Assessment

Wild

• Wild Level: Medium
• Number of Infections: More than 1000
• Number of Sites: More than 10
• Geographical Distribution: High
• Threat Containment: Moderate
• Removal: Moderate

Damage

• Damage Level: Low
• Large Scale E-mailing: Mass mailing worm
• Modifies Files: Renames specific Win32 programs to have a .vxd extension

Distribution

• Distribution Level: High
• Name of Attachment: Photo1.gif.pif
• Size of Attachment: 62,464

TECHNICAL DETAILS

W32.Stator@mm is a Borland Delphi program packed using ASPack. Upon execution it:

1. Renames the following files:
   • Notepad.exe -> Notepad.vxd
   • Control.exe -> Control.vxd
   • Mplayer.exe -> Mplayer.vxd
   • Winhlp32.exe -> Winhlp32.vxd
2. After renaming these files, W32.Stator@mm worm may then create copies of itself with the following names in the Windows folder:
   • Notepad.exe
   • Control.exe
   • Mplayer.exe
   • Winhlp32.exe
   • Ifnhlp.sys
3. The worm creates copies of itself in the WindowsSystem folder as:
   • Loadpe.com
   • Scanregw.exe
4. It may also rename other Win32 programs to have the .vxd file extension and create copies of itself using the original file names. Most likely, it tries to apply this method to Win32 programs that are loaded at startup from the registry or the StartUp folder.
5. In the following registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunServices
   
   the worm adds the following value:
   
   ScanRegistry
   
   This value points to the WindowsSystemScanregw.exe file that the worm created.
   
6. In the following registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionexplorer
   
   it adds the following value:
   
   PLC_Region
   
   This value contains a numeric value.
   
7. To mail itself out, it creates its own fake header structure, attempts to connect to an SMTP server in Russia, and mails itself out from there. The name of the file attachment is:
   
   Photo1.jpg.pif

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

To remove this worm, run LiveUpdate, undo the changes that the worm made to the registry, run a scan using the DOS scanner, and then rename the files that were renamed by the worm back to their original file names.

Run LiveUpdate
Run LiveUpdate to make sure that you have the most recent virus definitions before you begin the removal process.


To edit the registry
The worm modifies the registry such that an infected file is executed every time that you run a .exe file. Follow these instructions to fix this.

1. Copy Regedit.exe to Regedit.com:
Because the worm modified the registry so that you cannot run .exe files, you must first make a copy of the Registry Editor as a file with the .com extension, and then run that.

1. Do one of the following, depending on which operating system you are running:
   • Windows 95/98 users: Click Start, point to Programs, and click MS-DOS Prompt.
   • Windows ME users: Click Start, point to Programs, point to Accessories, and then click MS-DOS Prompt.
   • Windows NT/2000 users:
     1. Click Start, and click Run.
     2. Type the following and then press Enter:
        
        command
        
        A DOS window opens.
        
     3. Type the following and then press Enter:
        
        cd winnt
        
     4. Go on to the next step.
   • Windows XP users
     1. Click Start, and click Run.
     2. Type the following and then press Enter:
        
        command
        
        A DOS window opens.
        
     3. Type the following and then press Enter after each one:
        
        cd
        cd windows
        
     4. Go on to the next step.
        
2. Type the following and then press Enter:
   
   copy regedit.exe regedit.com
   
3. Type the following and then press Enter:
   
   start regedit.com
   

1. Proceed to the section "To edit the registry and remove keys and changes made by the worm" only after you have accomplished the previous steps.

NOTE: This will open the Registry Editor in front of the DOS window. After you finish editing the registry and have closed Registry Editor, close the DOS window.

2. To edit the registry and remove keys and changes made by the worm:

CAUTION: We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure you modify only the keys specified. Please see the document How to back up the Windows registry before proceeding.

1. Navigate to the following key:
   
   HKEY_CLASSES_ROOTexefileshellopencommand
   
2. In the right pane, double-click the value:
   
   (Default)
   
   The Edit string dialog box opens.
   
3. Modify the default entry, which was changed by the worm, so that the path and file name for the worm are removed. For example, you must change
   
   c:windowssystemloadpe.com" "%1" %*
   
   to the following:
   
   "%1" %*
   
   (That is, delete the entire contents of the Value data box, and then type the following characters: quote-percent-one-quote-space-percent-asterisk.)
   
   Value data as changed by the worm:
   
   
   Value data as it should be:
   
   
4. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunServices
   
5. In the right pane, delete the following value:
   
   ScanRegistry
   
   This value should point to the copy of the worm in the WindowsSystem folder.
   
   NOTE: Make sure that you are in the key specified. Do not delete the value named ScanRegistry that is in the following key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
6. Exit the Registry Editor.

To scan from DOS:
Determine the DOS name of the Norton AntiVirus folder, restart the computer, and scan from DOS:

1. Start Windows Explorer.
2. Follow the instructions for your installation:
   • If it is installed as part of Norton System Works:
     1. Browse to where Norton AntiVirus is installed. By default, this is C:Program FilesNorton System WorksNorton AntiVirus.
     2. Right-click the Norton SystemWorks folder, and click Properties.
     3. On the General tab, note the MS-DOS name (for example, NORTON~1). Write this down.
     4. Right-click the Norton AntiVirus folder, and click Properties.
     5. On the General tab, note the MS-DOS name (for example, NORTON~1). Write this down.
     6. Follow the instructions for your operating system:
        • Windows 95/98: Click Start, click Shut down, click Restart in MS-DOS mode, and then click OK. The computer restarts to a command prompt.
        • Windows Me: You must restart the computer using a Windows Me Startup disk. Read your Windows Me Help or the document How to Boot to DOS or open an MS-DOS prompt under Windows Millennium Edition.
     7. Type the following, pressing Enter after each one:
        
        NOTE: When typing the last command, type the MS-DOS name that you wrote down in step 4.
        
        cd
        cd progra~1
        cd norton~1
        cd norton~1
        
     8. Go on to step 3.
   • If Norton AntiVirus is installed by itself:
     1. Browse to where Norton AntiVirus is installed. By default, this is C:Program FilesNorton AntiVirus.
     2. Right-click the Norton AntiVirus folder, and click Properties.
     3. On the General tab, note the MS-DOS name (for example, NORTON~1). Write this down.
     4. Follow the instructions for your operating system:
        • Windows 95/98: Click Start, click Shut down, click Restart in MS-DOS mode, and then click OK. The computer restarts to a command prompt.
        • Windows Me: You must restart the computer using a Windows Me Startup disk. Read your Windows Me Help or the document How to Boot to DOS or open an MS-DOS prompt under Windows Millennium Edition
     5. Type the following, pressing Enter after each one:
        
        NOTE: When typing the last command, type the MS-DOS name that you wrote down in step 3.
        
        cd
        cd progra~1
        cd norton~1
        
        NOTE: If you see "Invalid directory" after typing any of these commands, Norton AntiVirus may have been installed to a different location. To find out the location, at the C: prompt type:
        
        dir /s /b avdx.exe
        
        When the correct path is found, substitute that path when typing the cd command shown here.
        
     6. Go on to step 3.
        
        
3. Type one of the following commands.
   
   CAUTION: This could take several hours or more on some computers. Do not attempt to stop the scan once it has started.
   
   NOTE: The DOS-based scanner can perform one of the following actions when it detects a virus:
   
   • To be prompted for any file that is detected as infected, type the following:
     
     navdx /a /doallfiles /prompt [Enter]
     
     You must press R)epair, D)elete or C)ontinue for each infected file. If you choose this option and NAV cannot repair an infected file, then you will see the message "Unable to repair the file," followed by the same three choices. In most cases you should then choose D)elete, unless you are sure that the file is not actually infected.
     
   • To repair any file that is detected as infected, type the following:
     
     navdx /a /doallfiles /repair [Enter]
     
     CAUTION: If NAV cannot repair a file and you choose this option, the file will be skipped. This means that infected files will still be on your system. If you choose this option, then you must run Navdx again, this time using the /delete switch, as shown in the previous example.
     
   • To delete any file that is detected as infected, type the following:
     
     navdx /a /doallfiles /delete [Enter]
     
     The disadvantage of this is that files that could be repaired will be deleted.
     
4. When the scan has finished, proceed to the next section.

To rename files:
You must rename the files that were renamed by the worm to have .vxd file extensions instead of .exe extensions:

1. Type the following, pressing Enter after each one:
   
   cd
   cd windows
   ren notepad.vxd notepad.exe
   ren control.vxd control.exe
   ren mplayer.vxd mplayer.exe
   ren winhlp32.vxd winhlp32.exe
   
   NOTE: If you installed Windows to a different location, make the appropriate substitution.
   
2. Restart the computer.
   
   

When Windows starts, start Norton AntiVirus and run a full system scan.