BAT.Batwin.Worm

SUMMARY

BAT.Batwin.Worm is a script worm that attempts to email itself to all addresses in the Microsoft Outlook Address Book. This threat may appear in email in the following format:

Subject: Newest Windows Security Patch!
Message:
A new Loveletter version is making the rounds. This version is able to steal your internet-access username and password. Here is the newest AntiVirus Patch against it.
Attachment: Bat.windows.bat

Protection

• Virus Definitions (LiveUpdate™ Weekly) July 22, 2002
• Virus Definitions (Intelligent Updater) July 22, 2002

TECHNICAL DETAILS

When BAT.Batwin.Worm runs, it does the following,

It copies itself as:

• C:Bat.windows.bat
• A:Bat.windows.bat

It then creates these files:

• C:Sig.sys (24 bytes)
• C:\%windir%StartmenuProgrammeAutostartWindows.vbs or C:<Current Folder>Msg (138 bytes)
• C:\%windir%Wyrm.vbs (692 bytes)

NOTES:

• %windir% is a variable. The worm locates the Windows folder (by default this is C:Windows or C:Winnt) and creates Wyrm.vbs in that location.
• Sig.sys, Windows.vbs and Msg are all text files and not viral; therefore, they are not detected by Symantec antivirus products. Delete those three files manually if your computer is infected with BAT.Batwin.worm.
• The worm first creates the file called Msg in the current folder, and then moves Msg to C:\%windir%StartmenuProgrammeAutostartWindows.vbs if the C:\%windir%StartmenuProgrammeAutostart folder exists.

The worm uses Microsoft Outlook to email itself to all addresses in the Outlook Address Book by using the C:\%windir%Wyrm.vbs file. The email message is in the following format:

Subject: Newest Windows Security Patch!
Message:
A new Loveletter version is making the rounds. This version is able to steal your internet-access username and password. Here is the newest AntiVirus Patch against it.
Attachment: Bat.windows.bat

The worm prepends itself to the C:\%windir%Win.ini file. After this occurs, on Windows 95/98/Me-based computers, the worm runs when you start Windows because the worm body contains the following section:

[windows]
load=c:at.windows.bat
run=C:WINDOWSSYSTEMcmmpu.exe
NullPort=None

The worm also attempts to delete the following files:

• C:ProgrammeNorton~1S32integ.dll
• C:ProgrammeF-Prot95Fpwm32.dll
• C:ProgrammeMcafeeScan.dat
• C:Tbavw95Tbscan.sig
• C:ProgrammeTbavTbav.dat
• C:TbavTbav.dat
• C:ProgrammeAvpersonalAntivir.vdf
• C:MircScript.ini
• C:Mirc32Script.ini
• C:Progra~1MircScript.ini
• C:Progra~1Mirc32Script.ini

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: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

Update the virus definitions, run a full system scan, and delete all files that are detected as BAT.Batwin.Worm. For details on how to do this, read the following instructions.

To scan with Norton AntiVirus and delete the infected files:

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
   • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
     
     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. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
   • NAV Consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • NAV Enterprise products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
3. Run a full system scan.
4. Delete all files that NAV detects as BAT.Batwin.Worm. Replace from a backup any files that the worm deleted, or reinstall them.