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Discovered: June 06, 2001
Updated: February 13, 2007 11:46:08 AM
Also Known As: DoS.Storm.Worm
Type: Worm

W32.Storm.Worm is a worm that seeks out Microsoft Internet Information Services (IIS) systems that have not applied the proper security patches. Any such systems that it finds are then infected with the worm. The payload of this worm performs a denial-of-service attack on http:/ /www.microsoft.com

Definitions dated prior to June 19, 2001, will detect this threat as DoS.Storm.Worm.

Antivirus Protection Dates

  • Initial Rapid Release version June 06, 2001
  • Latest Rapid Release version January 15, 2018 revision 004
  • Initial Daily Certified version June 06, 2001
  • Latest Daily Certified version August 09, 2016 revision 001

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

Technical Description

When this worm is run, it sets up a server FTP thread and starts to scan 10,000,000 IP addresses in an attempt to find a vulnerable system at one of the targeted addresses. The vulnerable systems that it targets are Microsoft IIS installations (versions 4 and 5) that do not have the security patches installed to cover the "Web Server Folder Traversal" security vulnerability as described in http://www.microsoft.com/technet/security/bulletin/MS00-078.asp .

Additional advice on securing IIS web servers is available from:


When the worm finds a vulnerable system, it copies itself to the targeted system and sets it up to automatically run the worm, effectively making that system a zombie that participates in the hacker's e-war. To make sure that the worm is run during the next system startup, the worm adds the value

666 c:\winnt\system32\storm\start.bat

to the following registry keys:



This worm has two payloads:
  • A denial-of-service attack is initiated against http:/ /www.microsoft.com.
  • An email bombing session is started that sends email messages containing an obscene message to gates@microsoft.com.


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.


Delete all files that are detected as W32.Storm.Worm and remove the added registry values.

Writeup By: Andre Post