VBS.Infi

SUMMARY

VBS.Infi is a Trojan Horse program that tries to take up disk space on every drive, including network drives, by making multiple copies of large files. This Trojan does not spread by itself, but may be sent as an email attachment, or may be spread by other means.

Protection

• Virus Definitions (LiveUpdate™ Weekly) March 27, 2002
• Virus Definitions (Intelligent Updater) March 26, 2002

TECHNICAL DETAILS

When VBS.Infi is executed, it checks every available drive starting with the current working folder and recursively processes subdirectories, by searching for files with the following extensions:

• .html
• .jpg
• .bmp
• .exe
• .com.
• .dat
• .mp3
• .avi

For each such file that VBS.Infi finds, it makes 31 copies in the same folder as the original file.

For example, the file, C:WindowsNotepad.exe, will be copied to:

• C:WindowsNotepad.exe0
• C:WindowsNotepad.exe1

and so on, up through C:WindowsNotepad.exe30.

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

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Run a full system scan and delete all the files detected as VBS.Infi.
3. Delete the files that VBS.Infi added.
   

For specific details on each of these steps, read the following instructions.

1. Updating the virus definitions
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 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).
• 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).
  
  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.

2. Scanning for and deleting the infected files

1. 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."
2. Run a full system scan.
3. If any files are detected as infected with VBS.Infi, click Delete.

3. Deleting the files
This step is only necessary if the script has been run.

To determine whether the script created any extra files on your computer:

1. Start Windows Explorer.
2. Click the View menu (Windows 95/98/NT) or the Tools menu (Windows Me/2000/XP), and then click Options or "Folder options."
3. Click the View tab.
4. Uncheck "Hide file extensions for known file types."
5. Do one of the following:
   • Windows 95/NT: Click "Show all files."
   • Windows 98: In the Advanced settings box, under the "Hidden files" folder, click Show all files.
   • Windows Me/2000/XP: Uncheck "Hide protected operating system files," and under the "Hidden files" folder, click "Show hidden files and folders."
6. Click Yes if you see a Warning dialog box.
7. Click Apply, and then click OK.
8. Follow the instructions for your operating system.
   

Windows 95/98/Me/NT/2000
1. Click Start, point to Find or Search, and then 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:
   
   *.exe0 *.exe1 *.exe2
   
   NOTE: Make sure that you type a space between the two sets of text.
   
   
4. Click Find Now or Search Now. If the search results show multiple copies of files that have the same filename, but with 0, 1, and 2 appended to the extension, it is likely that the script has run. Manually delete the files using Windows Explorer, or restore your system from a backup. Refer to the "Technical Details" section for details on other file extensions that may have been copied.

Windows XP
1. Click Start, and then click Search.
2. Click All files and folders.
3. In the "All or part of the file name" box, type, or copy and paste, the following:
   
   *.exe0 *.exe1 *.exe2
   
   NOTE: Make sure that you type a space between the two sets of text.
   
   
4. Verify that "Look in" is set to "Local Hard Drives" or to (C:).
5. Click "More advanced options."
6. Check "Search system folders."
7. Check "Search subfolders."
8. Click Search. If the search results show multiple copies of files that have the same filename, but with 0, 1, and 2 appended to the extension, it is likely that the script has run. Manually delete the files using Windows Explorer, or restore your system from a backup. Refer to the "Technical Details" section for details on other file extensions that may have been copied.