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security response
Category 4


Discovered on: November 24, 2001
Last Updated on: November 27, 2001 at 10:49:03 PM ZE8

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Due to the increased rate of submissions, Symantec Security Response has upgraded the threat level of this worm from level 3 to level 4 as of November 26, 2001.

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.

Type: Worm

Infection Length: 29,020 bytes

Virus Definitions: November 24, 2001

Threat Assessment:

High Low High




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%)

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 will shut down if the appropriate control bit is set.

If RAS support is present on the computer, then the worm will wait for an active RAS connection. When one is made, with a 33% chance, the worm will search for email addresses in *.ht* and *.asp in %Personal% and Internet Explorer %Cache%. If it finds addresses in these files, then it will send 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 will append two extensions. The first will be 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 sender's email address will have the "_" character prepended to it, to prevent replying to infected mails to warn the sender (eg becomes

After sending mail, the worm adds the value

Kernel32   kernel32.exe

to the registry key


This will run the worm the next time that you start Windows.

Removal instructions:

To remove this worm, follow the instructions for your operating system.

Basic instructions

Windows 95/98/Me

    1. Restart Windows in Safe Mode
    2. Run Norton AntiVirus and delete all files that are detected as W32.Badtrans.B@mm.
    3. Remove the value that it added to the registry.

Windows NT/2000/XP
    1. Restart Windows in VGA mode.
    2. Run Norton AntiVirus and delete all files that are detected as W32.Badtrans.B@mm.
    3. Remove the value that it added to the registry.

To remove files that cannot be deleted by NAV:
Follow the instructions for your version of Windows only if NAV could not delete files that it detected as infected with W32.Badtrans.B@mm.
    • Windows 95/98/Me
      1. Restart the computer in Safe Mode. For instructions on how to restart in Safe Mode, see the document How to restart Windows 9x or Windows Me in Safe Mode.
      2. Run the scan again, and delete any files detected as W32.Badtrans.B@mm.
      3. When the scan is finished, go on to the section To edit the registry.
    • Windows NT/2000/XP
      1. Press Ctrl+Alt+Delete one time.
      2. Click Task Manager.
      3. Click the Processes tab.
      4. Click the "Image Name" column header two times to sort the processes alphabetically.
      5. Scroll through the list and look for kernel32.exe. If you find the file, click it and then click End Process.
      6. Close the Task Manager.
      7. Run the scan again, and delete any files detected as W32.Badtrans.B@mm.
      8. When the scan is finished, go on to the section To edit the registry.

To 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. This document is available from the Symantec Fax-on-Demand system. In the U.S. and Canada, call (541) 984-2490, select option 2, and then request document 927002.
    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

    5. Click Registry, and then click Exit.

Additional information:


  • Corporate email filtering systems should block all email that have attachments with the extensions .scr and .pif.
  • Home users should not open any email that has an attachment in which the second extension is .pif or .scr. Any email that has such an attachment should be deleted.

Write-up by: Peter Ferrie



Pagina realizzata da Fracassi Andrea