Threat Explorer

The Threat Explorer is a comprehensive resource consumers can turn to for daily, accurate, up-to-date information on the latest threats, risks and vulnerabilities.

VBS.Pleh.A@mm

VBS.Pleh.A@mm

Discovered:
27 March 2001
Updated:
13 February 2007
Also Known As:
I-Worm.Pleh [Kaspersky], VBS_PLEH.A [Trend], VBS/Pleh [Sophos], VBS.Pleh [Computer Associates]
Systems Affected:
Windows

VBS.Pleh.A@mm sends itself to email addresses in the Microsoft Outlook address book. It overwrites files on local and remote drives, including files with the extensions .mp3, .pwd, .exe, .mp2, .doc, .avi, .mpeg, or .htm. The contents of these files are replaced with the source code of the worm, destroying the original contents.

Antivirus Protection Dates

  • Initial Rapid Release version 27 March 2001
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 27 March 2001
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date 27 March 2001
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

When executed, VBS.Pleh.A@mm does the following:
  1. It copies itself to the \Windows\System folder as Kernel.vbs and to the \Windows folder as Help.vbs.
  2. For each drive, including network drives, the virus attempts to infect files that have .vbs and .vbe extensions. The worm also searches for files with the extensions .mp3, .pwd, .exe, .mp2, .doc, .avi, .mpeg, or .htm, and overwrites them with viral code.

    CAUTION: Do not attempt to run files that have been overwritten or renamed by this worm. If you do, the worm is executed again.
  3. VBS.Pleh.A@mm uses MAPI calls to the Microsoft Outlook program and creates messages by going through all of the addresses in the Microsoft Outlook Address Book. The worm uses the Windows registry to keep track of those who have been sent email, so that each is sent only one message:

    Subject: I hate you

    Message: i think that you must see this file ,i insist.

    Attachment: help.vbs
  4. It creates the \Windows\Look Here folder.
  5. It then creates a text file in the \Look Here folder. This text file contains the following text:

    Hello!It so pity that i cant look at your face now,and do you know why ,because your machine was infected by Lynx[RAtm].Worm.Regards from Od.
  6. The worm also searches for the Logos.sys file, and deletes it if found.
  7. Next, it attempts to delete the folder C:\Windows\Ðàáî÷èé ñòîë.
  8. VBS.Pleh.A@mm modifies the C:\Autoexec.bat file in an attempt to format drive C the next time the computer is restarted.
  9. It configures itself to run each time the computer restarts by adding the line

    run=C:\Windows\help.vbs

    to the C:\Windows\Win.ini file.
  10. It also adds the value

    help     C:\WINDOWS\help.vbs

    to the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
    RunServices
  11. Once the worm has been executed, it displays the message

    Read Youmustread.txt file:-)


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.

To remove this worm, remove the changes it made to the Autoexec.bat and Win.ini files, delete any files detected as VBS.Pleh.A@mm, and remove the registry value that it added.

CAUTION: Do not restart the computer until you remove the commands from the Autoexec.bat file.

To edit the Autoexec.bat and Win.ini files:
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type sysedit and then click OK. The System Configuration Editor opens.
  3. In the Autoexec.bat file, look for the following lines and delete them:

    @cls
    @Please wait it can take only few minuts
    @format C:
  4. Click File, and click Save.
  5. Click the C:\Windows\Win.ini title bar.
  6. Located and delete the line

    run=C:\Windows\help.vbs
  7. Click File, and click Save.
  8. Close the System Configuration Editor.

To remove the worm files:
  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 VBS.Pleh.A@mm.

To edit the registry:

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

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
    RunServices
  4. In the right pane, delete the following value:

    help     C:\WINDOWS\help.vbs
  5. Click Registry, and click Exit to save the changes.

(Optional) Remove the folder
Using Windows Explorer, delete the C:\Windows\Look Here folder.


Writeup By: Douglas Knowles