VBS.Kidarcade.F

SUMMARY

VBS.Kidarcade.F is a virus based on Visual Basic Script (VBS). It has been put into an HTML page, and is on at least one Web site. The virus installs a Backdoor Trojan that allows unauthorized access to the infected computer.

Protection

• Virus Definitions (Intelligent Updater) June 13, 2001

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

VBS.Kidarcade.F is both a Visual Basic Script and a JavaScript virus. It utilizes the Scriptlet.TypLib ActiveX control, which allows local files to be created or modified. Microsoft has released a patch that eliminates security vulnerabilities in Scriptlet.TypLib. The patch removes the "safe for scripting" marking, thereby causing Internet Explorer to request confirmation from the user before loading the control. The patch is available at:

http://www.microsoft.com/technet/ie/tools/scrpteye.asp

VBS.Kidarcade.F performs the following actions:

1. If the security settings on the computer allow the scripts to run, then the HTML page will copy the file Welcome.hta to the WindowsStartUp folder. This file is a malicious Visual Basic Script, which will be executed every time that Windows starts.
   
2. When executed, the script drops the binary file 3ascii.bin. It then runs the DOS/Windows utility Debug.exe with the parameter "3ascii.bin" passed to it. 3ascii.bin is a binary file written in assembly language, and consists of the decoder and the encoded body of the Backdoor Trojan Cgibin.exe. Debug.exe reads the decoder instructions into memory and passes execution control to them. The decoder extracts the body of the Backdoor Trojan from 3ascii.bin and writes it as the Cgibin.exe file.
   
3. The script then moves the Backdoor Trojan to the Windows folder and runs it. The 3ascii.bin binary file is then deleted.
   
4. To enable the Backdoor Trojan to run at startup, the script creates the value
   
   SysWin   <Windows>cgibin.exe
   
   in the registry key
   
   HKEY_LOCAL_MACHINESoftwareMicrosoft
   WindowsCurrentVersionRun
   
5. When executed, the Backdoor Trojan copies itself to the Windows folder as Winasm32.exe. To enable itself to run at startup the Trojan creates the value
   
   RegistryKeyName1234567890  <Windows>Winasm32.exe
   
   in the following registry keys
   
   HKEY_LOCAL_MACHINESoftwareMicrosoft
   WindowsCurrentVersionRun
   
   HKEY_LOCAL_MACHINESoftwareMicrosoft
   WindowsCurrentVersionRunServices
   
6. Then the Backdoor Trojan sends the message "hey there, ive been committed" to the ICQ pager of the virus author. This tells the remote computer that the infected computer is ready for remote administration. It then starts to accept and perform the remote commands. The remote administration has full access to the file system of the infected computer. The Trojan permits the remote administrator to download or upload files from the remote computer, change the registry, and run commands and programs.
   
7. To prevent Windows from displaying the default .hta file extension, the script next creates the value
   
   NeverShowExt
   
   in the registry key
   
   HKEY_CLASSES_ROOThtafile
   
   and changes the value of
   
   HKEY_CLASSES_ROOThtafileDefaultIcon
   
   to
   
   SHELL32.DLL,44
   
8. The script then creates the Wininit.ini file in the Windows folder and writes the following lines in the file:
   
   [rename]
   NUL= <path> Welcome.hta

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 Trojan:

• Run Live update and then end all network connections, scan with Norton AntiVirus, and delete files detected as VBS.Kidarcade.F or Backdoor Trojan.
• Remove the text in the Wininit.ini file that refers to Welcome.hta.
• Remove the text in the Win.ini file that refers to Winasm32.exe.
• Remove the changes that were made to the registry.

The following sections offer detailed instructions.

To scan with Norton AntiVirus:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Make sure you have no network connections (unplug the network card and disconnect your dial-up connection, if any).
3. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
4. Delete any files detected as VBS.Kidarcade.F or Backdoor Trojan. If any files are detected as VBS.Kidarcade.F or Backdoor Trojan; then when the scan is finished, restart the computer and repeat the full system scan with NAV.

To edit the Wininit.ini file:

1. Click Start, point to Find or Search, and click Files or Folders.
2. Make sure that "Look in" is set to (C:) and that Include subfolders is checked.
3. In the "Named" or "Search for..." box, type--or copy and paste--the following file name:
   
   wininit.ini
   
4. Click Find Now or Search Now.
5. Double-click the Wininit.ini file that was found in the Windows folder. It opens in Notepad.
6. Look for the line <path>Welcome.hta, and delete it if it exists.
7. Save the changes, and close Notepad.

To edit the Win.ini file:

1. Click Start, point to Find or Search, and click Files or Folders.
2. Make sure that "Look in" is set to (C:) and that Include subfolders is checked.
3. In the "Named" or "Search for..." box, type--or copy and paste--the following file name:
   
   win.ini
   
4. Click Find Now or Search Now.
5. Double-click the Win.ini file that was found in the Windows folder. It opens in Notepad.
6. Look for the lines <path>winasm32.exe and delete them if they exist.
7. Save the changes, and close Notepad.

To edit the registry:

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. 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_CLASSES_ROOThtafile
   
4. In the right pane, delete the value
   
   NeverShowExt
   
5. Navigate to the key
   
   HKEY_LOCAL_MACHINESoftwareMicrosoft
   WindowsCurrentVersionRun
   
6. In the right pane, delete the values
   
   RegistryKeyName1234567890
   SysWin
   
7. Navigate to the key
   
   HKEY_LOCAL_MACHINESoftwareMicrosoft
   WindowsCurrentVersionRunServices
   
8. In the right pane, delete the value
   
   RegistryKeyName1234567890
   
9. Close the Registry Editor.