W32.Trilisa.B@mm

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Discovered: May 09, 2002
Updated: February 13, 2007 12:00:09 PM
Type: Trojan Horse, Worm
Systems Affected: Windows



W32.Trilisa.B@mm is a variant of W32.Trilisa@mm , and sends itself to all addresses in the Microsoft Outlook address book. The worm renames all files that are in the Windows or WINNT folder and that have the .exe or .scr file name extension to the extension .avp. It then copies itself as the original file name. For example, the worm will rename the clean Notepad.exe file as Notepad.avp. It will then copy itself as Notepad.exe.

NOTE: The worm cannot send itself to others through email because of a minor bug in the worm.

Antivirus Protection Dates

  • Initial Rapid Release version May 09, 2002
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version May 09, 2002
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date May 09, 2002

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

Writeup By: Gor Nazaryan

Discovered: May 09, 2002
Updated: February 13, 2007 12:00:09 PM
Type: Trojan Horse, Worm
Systems Affected: Windows


When W32.Trilisa.B@mm is executed, it does the following:

  1. It copies itself to:
    • C:\JKI.exe
    • %Windows%\JKI.exe
    • A:\JKI.exe
    • C:\AVP4.6.exe
  2. It creates the following Visual Basic Script (VBS) file:

    C:\Semen.vbs
  3. The Semen.vbs file sends email to all contacts in the Microsoft Outlook address book. The email has the following characteristics:

    NOTE:
    Due to a minor bug in the Semen.vbs, it cannot send email messages.

    Subject: Neue annoncierende Version des AVP
    Message:
    Neue annoncierende Version von Antivirus AVP,prft bitte Ost-Software
    Attachment:
    AVP4.6.exe
  4. The worm renames all files that are in the Windows or WINNT folder and that have the .exe or .scr extension to the .avp extension. It then copies itself as the original file name. For example the worm renames the clean Notepad.exe file as Notepad.avp. It then copies itself as Notepad.exe.
  5. The worm changes the (Default) value of the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

    to

    C:\Semen.vbs
  6. It changes the (Default) value of the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
    CurrentVersion\RunServices

    to

    C:\jki.exe
  7. Then the worm changes the (Default) value of the registry key

    HKEY_CLASSES_ROOT\exefile\shell\open\command

    with the (Default) value of

    C:\jki.exe "%1" %*"
  8. The worm then displays a message box with the following message:

    Tatsache durch Sherolx/Belgica, eine nacht sehr regnerisch

    When you click OK, the worm sleeps for two minutes and then shuts down the computer.


Recommendations

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.

Writeup By: Gor Nazaryan

Discovered: May 09, 2002
Updated: February 13, 2007 12:00:09 PM
Type: Trojan Horse, Worm
Systems Affected: Windows



Follow the instructions in each section in the order shown. We strongly recommend that you read and understand the entire procedure before proceeding.

To remove this worm, you must do the following:

  • Set Windows to show all files.
  • Copy Regedit.exe to Regedit.com. You'll only need to do this if you cannot start program files, or if you see the message "Windows cannot find wintask.exe."
  • Edit the registry and remove keys and changes made by the worm.
  • Run a full system scan and delete all files detected as W32.Trilisa.B@mm.
  • Rename the extension of every .avp file that is in the Windows or WINNT folder to either .scr or .exe, depending upon which file name extension the original file used. If there is any doubt as to the original extension of the file, we suggest renaming with the .exe extension.

NOTE: Because some of the infected files may be Windows files, if Windows does not work correctly, then it may be necessary to reinstall Windows.

For detailed instructions on how to remove the worm, see the sections that follow.

To set Windows to show all files:
  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.
    To copy Regedit.exe to Regedit.com:
    If you cannot start program files, or if you see the message "Windows cannot find wintask.exe," then you'll need to copy Regedit.exe to Regedit.com.
    1. Do one of the following, depending on which operating system you are running:
      • Windows 95/98/Me users: Click Start, point to Programs, and click MS-DOS Prompt.
      • Windows NT/2000/XP users:
        1. Click Start, and click Run.
        2. Click Browse, and browse to the \Winnt\system32 folder.
        3. Double-click the Command.com file, and then click OK.
    1. Type copy regedit.exe  regedit.com and press Enter.
    2. Type start regedit.com and press Enter.
    3. Proceed to the section "To edit the registry and remove keys and changes made by the worm."

    NOTE: This will open Registry Editor in front of the DOS window. After you finish editing the registry and have closed Registry Editor, close the DOS window.

    To edit the registry and remove keys and changes made by the worm:

    CAUTION : We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry can result in permanent data loss or corrupted files. Please make sure you modify only the keys specified in this document. For more information about how to back up the registry, please read How to back up the Windows registry before proceeding with the following steps. If you are concerned that you cannot follow these steps correctly, then please do not proceed. Consult a computer technician for more information.
    1. Start Registry Editor if necessary:
      • If you performed the procedure in the previous section, the Registry Editor is already open. Skip to step 4.
      • If it was not necessary to perform the procedures in the previous section, go on to step 2.
    2. Click Start, and click Run. The Run dialog box appears.
    3. Type regedit and click OK. Registry Editor opens.

      NOTE: If you see an error message or Registry Editor does not open, go back to and follow the instructions in the previous section.
    4. Navigate to and select the following key:

      HKEY_CLASSES_ROOT\exefile\shell\open\command

      CAUTION: The HKEY_CLASSES_ROOT key contains many subkey entries that refer to other file extensions. One of these file extensions is .exe. Changing this extension can prevent any files ending with an .exe extension from running. Make sure you browse all the way along this path until you reach the \command subkey.

      Modify the HKEY_CLASSES_ROOT\exefile\shell\open\command subkey that is shown in the following figure:

      <<=== NOTE: This is the key that you need to modify.
    5. In the right pane, double-click the (Default) value.
    6. Delete the current value data, and then type: "%1" %* (That is, type the following characters: quote-percent-one-quote-space-percent-asterisk.)

      NOTE: Registry Editor will automatically enclose the value in quotation marks. When you click OK, the (Default) value should look exactly like this:
      ""%1" %*"

      Make sure you completely delete all value data in the command key prior to typing the correct data. If a space is left at the beginning of the entry, any attempt to run program files will result in the error message, "Windows cannot find .exe." If this happens to you, start over at the beginning of this document, making sure to completely remove the current value data.
    7. Navigate to each of the following keys one at a time:

      HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

      HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
      CurrentVersion\RunServices
    8. For each key, in the right pane double-click the (Default) value.
    9. Delete the current value data so that the field is empty, as shown in the following figure:


    10. Click OK.
    11. Close the Registry Editor.

    To delete files that are detected as W32.Trilisa.B@mm:
    1. Obtain the most recent virus definitions. There are two ways to do this:
      • Run LiveUpdate. LiveUpdate 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. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
    3. Run a full system scan.
    4. Delete all files that are detected as W32.Trilisa.B@mm.

    To rename the .avp files:
    Files that have been changed by the worm are executable (program) and screen saver files. Because they all now have the same extension, it may be difficult to determine what the original extension was. It may be easier to simply reinstall programs that no longer work.

    NOTE: Because some of the infected files may be Windows files, if Windows does not work correctly, then it may be necessary to reinstall Windows.

    If Windows is working properly, follow the steps for your operating system to search for and rename files:

    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 file name:

      *.avp
    4. Click Find Now or Search Now.
    5. For each file that is found, right-click the file and click Rename. Then rename the file to either the .exe or .scr extension. For example: Rename Notepad.avp to Notepad.exe. If you are not sure whether the file is a program executable (.exe) or a screen saver file (.scr), then rename the file as .exe. This will allow any program executables to run correctly. At a later time, If you notice that a screen saver does not run correctly, then you can reinstall the screen saver program.

    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 file name:

      *.avp
    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.
    9. For each file that is found, right-click the file and click Rename. Then rename the file to either the .exe or .scr extension. For example: Rename Notepad.avp to Notepad.exe. If you are not sure whether the file is a program executable (.exe) or a screen saver file (.scr), then rename the file as .exe. This will allow any program executables to run correctly. At a later time, if you notice that a screen saver does not run correctly, then you can reinstall the screen saver program.


    Writeup By: Gor Nazaryan