W32.ExploreZip.F.Worm

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Discovered: September 11, 2000
Updated: February 13, 2007 11:34:16 AM
Also Known As: W32/ExploreZip.worm trojan, Worm.ExploreZip
Type: Worm



W32.ExploreZip.F.Worm is a variant of Worm.ExploreZip , a worm that contains a malicious payload. The worm uses Microsoft Outlook, Outlook Express, and Exchange to mail itself by replying to unread messages in the inbox. The email attachment is Zipped_files.exe, and its size is 210,432 bytes. The worm searches the mapped drives and networked computers for Windows installations, copies itself to the Windows folder of the remote computer, and modifies the Win.ini file.

Antivirus Protection Dates

  • Initial Rapid Release version September 12, 2000
  • Latest Rapid Release version March 03, 2008 revision 035
  • Initial Daily Certified version September 12, 2000
  • Latest Daily Certified version March 03, 2008 revision 037

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

Writeup By: Raul Elnitiarta

Discovered: September 11, 2000
Updated: February 13, 2007 11:34:16 AM
Also Known As: W32/ExploreZip.worm trojan, Worm.ExploreZip
Type: Worm


W32.ExploreZip.F.Worm has a different entry point and a different virtual size from the original variant. The new entry point contains a reference to the Initx.dat file. After that, the original ExploreZip routine is executed. The worm routine is identical to the original ExploreZip.Worm.

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: Raul Elnitiarta

Discovered: September 11, 2000
Updated: February 13, 2007 11:34:16 AM
Also Known As: W32/ExploreZip.worm trojan, Worm.ExploreZip
Type: Worm


To avoid restarting from a clean system disk, Symantec Security Response has provided a utility named KILL_EZ to remove the virus from memory. You can find additional information regarding this tool at the KILL_EZ Tool page .

To remove this worm manually:

  • Windows 9x
    Remove the line

    run=?\Explore.exe

    or

    run=?\_setup.exe

    from the Win.ini file.
  • Windows NT
    1. From the following registry key:

      HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows\Run

      remove the entry that refers to Explore.exe or _setup.exe.
    2. Delete the Explore.exe or _setup.exe file. You might need to restart first or end the process using Task Manager or Process View (if the file is currently in use).


Writeup By: Raul Elnitiarta