Backdoor.Doly

SUMMARY

The Backdoor.Doly virus is received in an email attachment named MyVid.exe.

Protection

• Virus Definitions (LiveUpdate™ Weekly) February 9, 2000
• Virus Definitions (Intelligent Updater) February 7, 2000

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When you click the file, nothing appears to happen. After it is run, however:

• If you attempt to start the Windows Registry Editor, you see the message "The Administrator has denied you permission to this service."
• If you are running Windows 98 and you try to run MSConfig, you cannot do so because the Msconfig.exe file has been deleted.

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 virus, please follow the instructions in each section.

NOTE: The procedure described in this document is complex and assumes that you are familiar with basic Windows and DOS procedures. If you are not, then we suggest that you obtain the services of a qualified computer consultant.

Start the computer in MS-DOS mode
The first part of the removal procedure must be performed in MS-DOS mode. Please follow these steps:

• Windows 95
  1. If the computer is on, then close all programs and, if possible, shut down Windows.
  2. Turn off the computer, and wait thirty seconds. You must turn off the power to clear memory. Do not simply press the reset button.
  3. Restart the computer, and watch the screen. When you see "Starting Windows 95," press F8.
  4. Select "Safe mode Command Prompt Only" from the startup menu, and then press Enter.
• Windows 98
  1. If the computer is on, then close all programs and, if possible, shut down Windows.
  2. Turn off the computer and wait thirty seconds. You must turn off the power to clear memory. Do not simply press the reset button.
  3. Restart the computer, and immediately press and hold down the Ctrl key until the Windows 98 startup menu appears.
  4. Select "Safe mode Command Prompt Only" from the startup menu, and then press Enter.

Remove infected files in MS-DOS mode
At the DOS prompt, which should appear similar to C:> , type the following commands in the sequence shown. Press Enter after each one.

NOTE: These instructions assume that the path to your Windows folder is C:Windows. If you installed Windows to a different folder, for example, C:Win95, then please modify the commands that refer to the Windows folder accordingly.

cd
attrib -r -s -h sys.lon
del sys.lon
cd windows
attrib -r -s -h win32ole.exe
del win32ole.exe
attrib -r -s -h wings32.reg
del wings32.reg
attrib -r -s -h asp4dos.com
del asp4dos.com
cd windowssystem
attrib -r -s -h wings32.drv
del wings32.drv
attrib -r -s -h kernal32.exe
del kernal32.exe
attrib -r -s -h qtjava.zip
del qtjava.zip
cd windowscookies
attrib -r -s -h iecookie.exe
del iecookie.exe
cd windowsstartm~1programsstartup
attrib -r -s -h mdn.exe
del mdn.exe
cd progra~1
attrib -r -s -h mdm.exe
del mdm.exe
cd
edit autoexec.bat (This will open the Autoexec.bat file in the DOS editor.)

Delete the following lines form the Autoexec.bat file:
lh c:windowsasp4dos.com
Set qtjava=c:windowssystemqtjava.zip
Set class path
Del Win.reg
cls
@echo off               copy c:sys.lon c:startm~1programsstartupmdn.exe

When you have finished deleting these lines, press Alt+F to access the File menu, and press S to save the file. Next, press Alt+F to access the File menu, and press X to exit the DOS editor.)

The files are now deleted from the computer. Please restart the computer, and allow Windows to load. When Windows finishes loading, you must restore the files that were deleted by the virus.

Restore files
Please see the instructions for your version of Windows.

• Windows 98
  If you are running Windows 98, you must restore the MSconfig.exe and Regedit.exe files. Please follow these steps:
  1. Insert the Windows 98 CD into the CD-ROM drive. If the installation splash screen appears, click Exit.
  2. Click Start, and click Run.
  3. Type sfc and then click OK.
  4. Click "Extract One File from Installation Disk."
  5. In the Files to extract box, type Msconfig.exe and then click Start.
  6. In the "Restore From" box, browse to the x:Win98 folder, where x is the letter of your CD-ROM drive.
  7. In the "Save File In" box, type C:WindowsSystem and click OK, and then click OK again.
  8. Repeat steps 3 through 7, substituting the Regedit.exe file in step 5.
• Windows 95
  If you are running Windows 95, you must restore the Regedit.exe file. Please follow these steps:
  1. Insert the Windows 98 CD into the CD-ROM drive. If the installation splash screen appears, then click Exit.
  2. Click Start, and click Run.
  3. Type command and then click OK. A DOS window opens.
  4. Type the following commands, pressing Enter after each one:
     
     cd windows
     extract /a x:win95win95_02.cab regedit.exe /l c:windows (where x is the letter of your CD-ROM drive)
     
  5. You should see the message "Extraction Complete."
  6. Type exit and then press Enter to return to Windows.

Remove the Registry entries
You must remove registry entries that were added by the virus. Please follow these steps:

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 specified keys. Please see the document How to back up the Windows registry before proceeding.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Click the Edit menu, and click Find.
4. In the Find What box, type mdm.exe and then click Find Next.
5. When an entry is found that refers to mdm.exe, select it, press Delete, and then click Yes to confirm.
6. Press F3 to search again for the same file. Delete all found entries until you are finished searching the registry. There should be three entries.
7. Exit the Registry Editor.
8. Repeat steps 1 through 7, but replace the text in step 4 with asp4dos.com
9. Repeat steps 1 through 7, but replace the text in step 4 with mstesk

Backdoor.Doly has been removed from your system. Perform a full system scan using Norton AntiVirus.