W32.Explet.A@mm

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Discovered: June 02, 2004
Updated: February 13, 2007 12:23:57 PM
Also Known As: I-Worm.Plexus.a [Kaspersky], WORM_PLEXUS.A [Trend], Win32.Mimail.W [Computer Assoc, W32/Plexus@MM [McAfee]
Type: Worm
Systems Affected: Windows
CVE References: CAN-2003-0533 CAN-2003-0352



W32.Explet.A@mm is a mass-mailing worm that also spreads through network shares and the Kazaa file-sharing network. The worm exploits the Microsoft Windows LSASS Buffer Overrun Vulnerability (described in Microsoft Security Bulletin MS04-011 ) and the DCOM RPC vulnerability (described in Microsoft Security Bulletin MS03-026 ) through TCP ports 135 and 445. It may also lower security settings and download remote files.

Antivirus Protection Dates

  • Initial Rapid Release version June 03, 2004
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version June 03, 2004
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date June 07, 2004

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

Writeup By: Yana Liu

Discovered: June 02, 2004
Updated: February 13, 2007 12:23:57 PM
Also Known As: I-Worm.Plexus.a [Kaspersky], WORM_PLEXUS.A [Trend], Win32.Mimail.W [Computer Assoc, W32/Plexus@MM [McAfee]
Type: Worm
Systems Affected: Windows
CVE References: CAN-2003-0533 CAN-2003-0352


When W32.Explet.A@mm runs, it does the following:

  1. If the worm's file name does not contain upu.exe, it displays a fake message whose title is "Error", and message is one of the following,

    • File is corrupted.
    • Could not initialize installation. File size expected=26523, size returned=26344.
    • Pack method not implemented.
    • CRC checksum failed.

  2. Copies itself as the following:

    • %Windir%\system32\upu.exe

      Note: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.

  3. Creates the following files:

    • %Windir%\svchost.exe (Attributes are set to hidden, archive, and system.)
    • %Windir%\a (An FTP script.)
    • %Windir%\system32\setupex.exe ( A copy of Backdoor.Nibu.G.)

  4. Executes its component %Windir%\svchost.exe.

  5. Executes the file %Windir%\system32\setupex.exe.

  6. Creates the mutex "Expletus", so that allows only one instance of the worm is run.

  7. Adds the value:

    "NvClipRsv" = "%Windir%\svchost.exe"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

    so that the worm runs every time Windows starts.

  8. Retrieves Kazaa shared folder by querying the following subkey:

    HKEY_CURRENT_USER\Software\Kazaa\Transfer\DlDir0

  9. Copies itself to the Kazaa shared folder as one of the following:

    • AVP5.xcrack.exe
    • hx00def.exe
    • ICQBomber.exe
    • InternetOptimizer1.05b.exe
    • Shrek_2.exe
    • UnNukeit9xNTICQ04noimageCrk.exe
    • YahooDBMails.exe

  10. Copies itself to network shares as one of the following:

    • AVP5.xcrack.exe
    • hx00def.exe
    • ICQBomber.exe
    • InternetOptimizer1.05b.exe
    • Shrek_2.exe
    • UnNukeit9xNTICQ04noimageCrk.exe
    • YahooDBMails.exe

  11. Overwrites the hosts file with the following lines:

    127.0.0.1  downloads-eu1.kaspersky-labs.com
    127.0.0.1  downloads2.kaspersky-labs.com
    127.0.0.1  downloads4.kaspersky-labs.com
    127.0.0.1  downloads1.kaspersky-labs.com
    127.0.0.1  downloads-us1.kaspersky-labs.com

  12. Attempts to propagate by exploiting the Microsoft Windows LSASS Buffer Overrun Vulnerability (described in Microsoft Security Bulletin MS04-011) and the DCOM RPC vulnerability (described in Microsoft Security Bulletin MS03-026) through TCP ports 135 and 445.

  13. Listens on TCP port 1250. If a connection is established, the worm can download a file from the remote computer and save it as %Temp%\_up.exe. The worm then executes the file.

  14. Runs an FTP server on a random TCP port. If a connection is established, it sends the file %Windir%\a to the remote computer and instructs the remote computer to connect back and upload the file %Windir%\system32\upu.exe.

  15. Retrieves email address from files with .htm, .html, .php, .tbb, and .txt extensions on all fixed drives from C through Y.

    The worm avoids email addresses that contain the following strings:

    • .gov
    • .mil
    • abuse
    • accoun
    • acketst
    • admin
    • anyone
    • arin.
    • berkeley
    • borlan
    • bsd
    • bsd
    • bugs
    • ca
    • certific
    • contact
    • example
    • feste
    • fido
    • foo.
    • fsf.
    • gnu
    • gold-certs
    • google
    • google
    • gov.
    • help
    • hotmail
    • iana
    • ibm.com
    • icrosof
    • icrosoft
    • ietf
    • info
    • inpris
    • isc.o
    • isi.e
    • kernel
    • linux
    • linux
    • listserv
    • math
    • me
    • mit.e
    • mozilla
    • msn.
    • mydomai
    • mysqlruslis
    • no
    • nobody
    • nodomai
    • noone
    • not
    • nothing
    • ntivi
    • page
    • panda
    • pgp
    • postmaster
    • privacy
    • rating
    • rfc-ed
    • ripe.
    • root
    • samples
    • secur
    • secur
    • sendmail
    • service
    • site
    • soft
    • somebody
    • someone
    • sopho
    • spa
    • spam
    • submit
    • subscribe
    • support
    • syma
    • tanford.e
    • the.bat
    • unix
    • unix
    • usenet
    • utgers.ed
    • webmaster
    • www
    • you
    • your

  16. Uses its own SMTP engine to send itself to the email addresses that it finds. The email has the following characteristics:
    Subject: RE: order
    Message:
    Hi.
    Here is the archive with those information, you asked me.
    And don't forget, it is strongly confidencial!!!
    Seya, man.

    P.S. Don't forget my fee ;)
    Attachment: SecUNCE.exe

    Subject: For you
    Message:
    Hi, my darling :)
    Look at my new screensaver. I hope you will enjoy...
    Your Liza
    Attachment: AtlantI.exe

    Subject: Hi, Mike
    Message:
    My friend gave me this account generator for [http://]www.pantyola.com/[REMOVED] I wanna share it with you :)
    And please do not distribute it. It's private.
    Attachment: AGen1.03.exe

    Subject: Good offer.
    Message:
    Greets! I offer you full base of accounts with passwords of mail server yahoo.com. Here is archive with small part of it. You can see that all information is real. If you want to buy full base, please reply me...
    Attachment: demo.exe

    Subject: RE:
    Message:
    Hi, Nick. In this archive you can find all those things, you asked me.

    See you. Steve
    Attachment: release.exe

    Note: The From address is spoofed. The worm may choose the From address from a predetermined list, from addresses found on the compromised computer, or it may generate a random From address.


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: Yana Liu

Discovered: June 02, 2004
Updated: February 13, 2007 12:23:57 PM
Also Known As: I-Worm.Plexus.a [Kaspersky], WORM_PLEXUS.A [Trend], Win32.Mimail.W [Computer Assoc, W32/Plexus@MM [McAfee]
Type: Worm
Systems Affected: Windows
CVE References: CAN-2003-0533 CAN-2003-0352


The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Remove all the entries that the risk added to the hosts file.
  3. Update the virus definitions.
  4. Run a full system scan and delete all the files detected.
  5. Delete any values added to the registry.
For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
Note:
When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).

2. To remove all the entries that the risk added to the hosts file
  1. Navigate to the following location:

    • Windows 95/98/Me:
      %Windir%
    • Windows NT/2000/XP:
      %Windir%\System32\drivers\etc

      Notes:
    • The location of the hosts file may vary and some computers may not have this file. There may also be multiple copies of this file in different locations. If the file is not located in these folders, search your disk drives for the hosts file, and then complete the following steps for each instance found.
    • %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows (Windows 95/98/Me/XP) or C:\Winnt (Windows NT/2000).

  2. Double-click the hosts file.
  3. If necessary, deselect the "Always use this program to open this program" check box.
  4. Scroll through the list of programs and double-click Notepad.
  5. When the file opens, delete all the entries added by the risk. (See the Technical Details section for a complete list of entries.)
  6. Close Notepad and save your changes when prompted.

3. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the document: Virus Definitions (LiveUpdate).
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the document: Virus Definitions (Intelligent Updater).

    The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.


4. To scan for and delete the infected files
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected, click Delete.

Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode . Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [File path]
Message body: Windows cannot find [file name]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.


5. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. For instructions refer to the document: How to make a backup of the Windows registry.
  1. Click Start > Run.
  2. Type regedit
  3. Click OK.

    Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.

  4. Navigate to the subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

  5. In the right pane, delete the value:

    "NvClipRsv" = %Windir%\svchost.exe"

  6. Exit the Registry Editor.


Writeup By: Yana Liu