BAT.Black

SUMMARY

This is a batch file virus that appends itself to the C:Autoexec.bat file and prepends itself to the C:WindowsWin.ini file. The file name of the batch file is BlackDay.bat. Due to bugs in the virus code, some parts are not executed.

Protection

• Virus Definitions (Intelligent Updater) May 24, 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
• Deletes Files: del c: _onlineonline.exe del c:acrobatxeaderacrord32.exe del c:coreldraw70programsphotopnt.exe del c:winzipwinzip32.exe deltree /y c:windowsdesktop deltree /y c:eigene~1 deltree /y c:windowssendto deltree /y c:programme deltree /y c:programs deltree /y c:windows
• Modifies Files: Autoexec.bat, Win.ini

Distribution

• Distribution Level: Low
• Target of Infection: Autoexec.bat and Win.ini

TECHNICAL DETAILS

When BlackDay.bat is executed, it does the following:

1. It creates the C:\_bd-ptrr.bat file and sets its attribute to hidden.
2. It searches the folder that contains BlackDay.bat and its parent folder for .bat files, and appends itself to any that are found.
3. It copies itself as C:WindowsSystemBlackDay.bat with a hidden attribute.
4. The virus prepends itself to the C:WindowsWin.ini. (This occurs only if the virus file is named BlackDay.bat. If the batch file has been renamed to anything else, the virus will not be prepended to the Win.ini file.)
5. The virus then searches for the last .exe or .com file in the folder that contains BlackDay.bat, renames the file by prepending the letter V to it, and adds the hidden attribute to it. (If the file name is Command.com, however, it is not renamed.)
6. It attempts to delete the following files:
   • C:ProgrammeNorton~1S32integ.dll
   • C:T_onlineOnline.exe
   • C:AcrobatxReaderAcrord32.exe
   • C:CorelDraw70ProgramsPhotopnt.exe
   • C:WinzipWinzip32.exe
7. It then deletes all files and subfolders from the following folders using the deltree /y command:
   • C:WindowsDesktop
   • C:Eigene~1
   • C:WindowsSendto
   • C:Programme
   • C:Programs
   • C:Windows

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

NOTE: If the virus has executed, you may first have to reinstall Windows.

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
3. Delete any files detected as BAT.Black, with the exception of the Win.ini or Autoexec.bat files if they are detected.
4. If you are familiar with what should be in the Win.ini or Autoexec.bat files, open those files in a text editor and remove the text that the virus added; otherwise, replace them from a clean backup.
5. Using Windows Explorer, delete the C:_bd-ptrr.bat file, if it exists.
6. Replace any files that were deleted by the virus.