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Discovered: September 03, 2001
Updated: February 13, 2007 11:50:20 AM
Also Known As: W32.Urgent.Worm@mm, I-Worm.Apost [Kaspersky], W32/Apost-mm, W32/Apost-A [Sophos], WORM_APOST.A [Trend], Win32.Apost [Computer Associat, W32/APost@MM [McAfee]
Type: Worm
Systems Affected: Windows

NOTE: The worm was previously known as W32.Urgent.worm@mm. Due to a decrease in submissions, the threat level has been downgraded from 3 to 2.

This worm is a Visual Basic Application that arrives as the attachment Readme.exe. It requires the Microsoft Visual Basic Runtime Libraries to replicate.

The body of the email asks the recipient to review the attachment, but after it has been viewed it copies itself to the system and spreads itself to everyone in the Microsoft Outlook address book.

Antivirus Protection Dates

  • Initial Rapid Release version September 04, 2001
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version September 04, 2001
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date September 04, 2001

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

Technical Description

This worm arrives as an email message in the following format:

Subject: As per your request!
Message: Please find attached file for your review. I look forward to hear from you again very soon.  Thank you.
Attachment: Readme.exe

If the Readme.exe file is executed, the worm performs the following actions:

  1. It creates a copy of itself in the \Windows folder, as Readme.exe.
  2. It then creates the value

    macrosoft    C:\Windows\readme.exe

    in the registry key


    so that the worm runs each time that you start Windows.
  3. The worm then writes a copy of itself into the root of all drives (this includes floppy drives, Zip drives, and network drives).
  4. It emails itself to all the contacts in the Microsoft Outlook address book.
  5. It then displays the message:

    and waits for you to click Open. When you click Open, it repeats the previously mentioned steps and then displays the following fake error message:

  6. It then quits.

NOTE: Because this worm activates its insertion and emailing routine twice, a recipient will likely will get at least two emails with this worm as an attachment.


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 the worm, delete files that are detected as W32.Apost.Worm@mm and remove the registry entry that it added.

To remove the worm:

  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. Be sure that NAV is configured to scan all files.
  3. Delete all files that are detected as W32.Apost.Worm@mm.

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.
  1. Navigate to and select the following key:

  2. In the right pane, look for and select the value

    macrosoft     C:\Windows\readme.exe
  3. Press Delete, and then click Yes to confirm.
  4. Exit the Registry Editor.

Writeup By: Atli Gudmundsson