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Discovered: April 08, 2002
Updated: February 13, 2007 11:38:41 AM
Also Known As: W32.Aphex@mm, Bloodhound.VBS.Worm, I-Worm.Aplore [AVP], W32/Aplore-A [Sophos], W32/Aplore@MM [McAfee], Win32.Aphex [CA], WORM_APLORE.A [Trend], W32/Explorer [Panda]
Type: Worm
Systems Affected: Windows

W32.Aplore@mm is a mass-mailing worm that attempts to spread using email, IRC, and AOL Instant Messenger (AIM).

The worm sends an email that contains an attachment, Psecure20x-cgi-install.version.6.01.bin.hx.com, to all addresses that it finds in the Microsoft Outlook address book.

When connected to IRC or AIM, the worm sends a Web link to IRC channels or AIM contacts which references an .html file that was dropped on the infected computer. This file displays as a Web page, which asks the visitor to run a copy of the worm.

Definitions dated prior to April 8, 2002, may detect the Email.vbs file as Bloodhound.VBS.Worm.

  • Definitions dated prior to April 9, 2002, will detect this as W32.Aphex@mm.

Antivirus Protection Dates

  • Initial Rapid Release version April 08, 2002
  • Latest Rapid Release version December 05, 2017 revision 021
  • Initial Daily Certified version April 08, 2002
  • Latest Daily Certified version December 06, 2017 revision 001
  • Initial Weekly Certified release date April 10, 2002

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

Technical Description

When the worm is executed by running the file Psecure20x-cgi-install.version.6.01.bin.hx.com, it does the following:

  1. It copies itself as:
    • \%System%\Explorer.exe
    • \%System%\Psecure20x-cgi-install.version.6.01.bin.hx.com

      NOTE: %System% is a variable. The worm locates the \Windows\System folder (by default this is C:\Windows\System or C:\Winnt\System32) and copies itself to that location.
  2. It adds the value

    Explorer       %SYSTEM%\Explorer.exe

    to the registry key


    so that it runs when you start Windows.
  3. Next, it drops the file \%System%\Email.vbs. It then uses Microsoft Outlook to spread itself. The email has the following characteristics:

    Subject: .
    Message: .
    Attachment: Psecure20x-cgi-install.version.6.01.bin.hx.com

    NOTE: The subject and message each consist of only a period.
  4. It drops the file \%System%\Index.html. It then attempts to run Psecure20x-cgi-install.version.6.01.bin.hx.com from the System folder by using a refresh tag in the dropped .html file. The following .html message appears:

    Browser Plugin Required:

    You may need to restart your browser for changes to take affect.
    Security Certificate by Verisign 2002.
    MD5: 9DD756AC-80E057FC-E00703A2-F801F2E3

    Click HERE and choose "Run" to install.
  5. It drops the file \Windows\Aphex.jpg.
  6. Finally, it attempts to spread itself using IRC or AOL Instant Messenger ()AIM.

AOL Instant Messenger (AIM) functionality
Once the worm is active on the infected computer, it acts as an HTTP server on port 8180. This server hosts one Web page. The page displays the text that is mentioned in step 4 of the previous section.

The worm waits for you to connect to AIM; it then sends one of the following one-line messages to your AIM contacts:
  • btw, download this,
  • I wanted to show you this,
  • please check out,
  • hey go to,
  • see if you can get this to work,
  • this is cool,
  • tell me what you think about,
  • try this,
  • I almost forgot about,
  • I like this,
  • what about,
  • have you seen,
  • interestin,
  • lol,
  • wow,
  • whoa,
  • neat,
  • cool,
  • hmm,
  • psst,
  • hehe,
  • haha,
  • silly,
  • weird,

The message also includes a link, which references the hosted Web page, to the (now infected) computer. This functions only with the AOL software that is used with an AOL subscription. This does not function with the stand-alone AIM client.


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.


NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Update the virus definitions, and then restart the computer in Safe mode. Run a full system scan, and delete all files that are detected as W32.Aplore@mm.
  2. Delete the value

    Explorer       %SYSTEM%\Explorer.exe

    from the registry key

For details on how to do this, read the following instructions.

To scan for and delete the infected files:
  1. Obtain the most recent virus definitions. There are two ways to do this:
    • Run LiveUpdate, which 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. Restart the computer in Safe mode. All Windows 32-bit operating systems except Windows NT can be restarted in Safe mode. For instructions on how to do this, read the document How to start the computer in Safe Mode.
  3. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
  4. Run a full system scan.
  5. If any files are detected as infected by W32.Aplore@mm, click Delete.

To edit the registry:

CAUTION : We strongly recommend that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
  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:

    Explorer       %SYSTEM%\Explorer.exe
  5. Exit the Registry Editor.

Writeup By: Kaoru Hayashi