Discovered: November 24, 2001
Updated: February 13, 2007 11:37:49 AM
Also Known As: I-Worm.BadtransII [KAV], Badtrans.B@mm [Norman], W32/Badtrans.B [Panda], WORM_BADTRANS.B [Trend], W32/Badtrans-B [Sophos], W32/Badtrans.B@mm [F-Secure], W32/BadTrans@MM [McAfee], Win32.Badtrans.29020 [CA], Worm/Badtrans.B [Vexira]
Type: Worm
Systems Affected: Windows
CVE References: CVE-2001-0154

Due to a decreased rate of submissions, Symantec Security Response has downgraded the threat level of this worm from Category 3 to Category 2 as of May 5, 2003.

W32.Badtrans.B@mm is a MAPI worm that emails itself out using different file names. It also creates the file \Windows\System\Kdll.dll. It uses functions from this file to log keystrokes.

Antivirus Protection Dates

  • Initial Rapid Release version November 24, 2001
  • Latest Rapid Release version November 02, 2019 revision 007
  • Initial Daily Certified version November 24, 2001
  • Latest Daily Certified version November 04, 2019 revision 050
  • Initial Weekly Certified release date November 24, 2001

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Technical Description

This worm arrives as an email with one of several attachment names and a combination of two appended extensions. It contains a set of bits that control its behavior:
001 Log every window text
002 Encrypt keylog
004 Send log file to one of its addresses
008 Send cached passwords
010 Shut down at specified time
020 Use copyname as registry name (else kernel32)
040 Use kernel32.exe as copyname
080 Use current filename as copypath (skips 100 check)
100 Copy to %system% (else copy to %windows%)

NOTE : If Norton AntiVirus detects this in an email message as W32.Badtrans@mm.enc (not as W32.Badtrans.B@mm), this is the detection for the MIME-encoded exploit in the body of the email, and it is harmless as long as the attachment has been deleted. We recommend that you delete messages detected as W32.Badtrans.B@mm.enc and notify the person who sent it to you. We also strongly recommend that you run a full system scan to make sure that no other infection exists.

For additional information on .enc detections, read the document What is an .enc detection?

When it is first executed, it copies itself to %System% or %Windows% as Kernel32.exe, based on the control bits. Then it registers itself as a service process (Windows 9x/Me only). It creates the key log file %System%\Cp_25389.nls and drops %System%\Kdll.dll which contains the key logging code.

NOTE: %Windows% and %System% are variables. The worm locates the \Windows folder (by default this is C:\Windows or C:\Winnt) or the \System folder (by default this is C:\Windows\System or C:\Winnt\System32) and copies itself to that location.

A timer is used to examine the currently open window once per second and to check for a window title that contains any of the following as the first three characters:

  • LOG
  • PAS
  • REM
  • CON
  • TER
  • NET

These texts form the start of the words LOGon, PASsword, REMote, CONnection, TERminal, NETwork. There are also Russian versions of these same words in the list. If any of these words are found, then the key logging is enabled for 60 seconds. Every 30 seconds, the log file and the cached passwords are sent to one of these addresses or some others which are currently not operational:

After 20 seconds, the worm shuts down if the appropriate control bit is set.

If RAS support is present on the computer, then the worm waits for an active RAS connection. When such a connection is made, with a 33-percent chance, the worm searches for email addresses in *.ht* and *.asp in %Personal% and Internet Explorer %Cache%. If it finds addresses in these files, then it sends mail to those addresses using the victim's SMTP server. If this server is unavailable, the worm will choose from a list of its own. The attachment name will be one of the following:
  • Pics
  • images
  • New_Napster_Site
  • news_doc
  • YOU_are_FAT!
  • stuff
  • Card
  • Me_nude
  • Sorry_about_yesterday
  • info
  • docs
  • Humor
  • fun

In all cases, MAPI will also be used to find unread mail to which the worm will reply. The subject will be "Re:". In that case, the attachment name will be one of the following:
  • PICS
  • New_Napster_Site
  • CARD
  • Sorry_about_yesterday
  • DOCS
  • FUN

In all cases, the worm appends two extensions. The first is one of the following:
  • .doc
  • .mp3
  • .zip

The second extension that is appended to the file name is one of the following:
  • .pif
  • .scr

The resulting file name would look similar to CARD.doc.pif or NEWS_DOC.mp3.scr.

If SMTP information can be found on the computer, then it will be used for the From: field. Otherwise, the From: field will be one of these:
  • "Mary L. Adams" <>
  • "Monika Prado" <>
  • "Support" <>
  • " Admin" <>
  • " Administrator" <>
  • "Joanna" <>
  • "Mon S" <>
  • "Linda" <>
  • " Andy" <>
  • "Kelly Andersen" <>
  • "Tina" <>
  • "Rita Tulliani" <>
  • " Anna" <>

Email messages use the malformed MIME exploit to allow the attachment to execute in Microsoft Outlook without prompting. For information on this, go to:

The worm writes email addresses to the %System%\Protocol.dll file to prevent multiple emails to the same person. Additionally, the underscore ( _ ) character is prepended to the sender's email address, which prevents replying to infected mails to warn the sender (for example, becomes

After sending the mail, the worm adds the value

Kernel32   kernel32.exe

to the registry key


This causes the worm to run the next time that you start Windows. This value can differ based on the control bits mentioned previously.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • 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.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a 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.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. 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.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.


The preferred way to remove this worm is to use the W32.Badtrans.B@mm Removal Tool . If for any reason you cannot obtain the tool, you must remove the worm manually.

Manual removal

An online tutorial on how to manually remove W32.Badtrans.B@mm is available here .

To remove this worm manually, you must first remove the worm files and then reverse the change that it made to the registry.

Remove the worm files
Follow the instructions for your version of Windows.

Windows 95/98/Me/2000/XP
Because the worm file may be in use, you must in most cases restart in Safe mode before Norton AntiVirus can delete it.

CAUTION: For Windows Me or Windows XP users only. If you are running Windows Me or Windows XP, follow the instructions in the section System Restore option in Windows Me or System Restore option in Windows XP that is located at the end of this document before you begin the removal procedure.

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Restart the computer in Safe Mode. For instructions on how to do this, read the document for your operating system:
  3. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  4. Run a full system scan.
  5. Write down the names of any files that are detected as W32.Badtrans.B@mm, and then delete them.
  6. When the scan is finished, go on to the section Edit the registry.

Windows NT
Because the worm file may be in use, you must in most cases End Process on it before Norton AntiVirus can delete it.
  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Press Ctrl+Alt+Delete one time.
  3. Click Task Manager.
  4. Click the Processes tab.
  5. Click the "Image Name" column header two times to sort the processes alphabetically.
  6. Scroll through the list and look for Kernel32.exe. If you find the file, click it and then click End Process.
  7. Close the Task Manager.
  8. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  9. Run a full system scan.
  10. Write down the names of any files that are detected as W32.Badtrans.B@mm, and then delete them.
  11. When the scan is finished, go on to the section Edit the registry.

Edit the registry:

CAUTION : We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure that you modify only the keys that are specified. Please see the document How to back up the Windows registry before you proceed.
  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 following key:

  4. In the right pane, delete the following value:

    Kernel32   kernel32.exe

    CAUTION: The reference to Kernel32 is the most common value that is added by the worm, but it is not the only one possible. In some cases, it may not be there. In addition to looking for and deleting this value, you must also look for values that refer to any file names that were detected as infected by this worm when you ran the full system scan. All such values must be deleted.
  5. Click Registry, and then click Exit.
  6. Restart the computer.
  7. To make sure that all files have been removed, start Norton AntiVirus and run another full system scan.

Quarantined files
If you have quarantined files when they were detected by Norton AntiVirus, rather then deleting them, read the document What to do after you quarantined a file .

System Restore option in Windows Me/XP
Windows Me and Windows XP users should temporarily turn off System Restore. This feature, which is enabled by default, is used by Windows Me/XP to restore files on your computer in case they become damaged. When a computer is infected with a virus, worm, or Trojan, it is possible that the virus, worm, or Trojan could be backed up by System Restore. By default, Windows prevents System Restore from being modified by outside programs. As a result, there is the possibility that you could accidentally restore an infected file, or that on-line scanners would detect the threat in that location. For instructions on how to turn off System Restore, read your Windows documentation or one of the following articles:
For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article Anti-Virus Tools Cannot Clean Infected Files in the _Restore Folder , Article ID: Q263455.

Writeup By: Peter Ferrie