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Discovered: February 13, 2004
Updated: February 13, 2007 12:19:00 PM
Type: Trojan Horse
Systems Affected: Windows

Bloodhound.Exploit.6 is a heuristic detection for exploits of a Microsoft Internet Explorer vulnerability. This vulnerability was discovered in February 2004.

The vulnerability results from the incorrect handling of HTML files embedded in CHM files. (CHM is the Microsoft-compiled HTML help format.)

For more information, and to download a patch for the vulnerability, read Microsoft Security Bulletin MS04-013 .

The following information is provided for your convenience and is for Internet Explorer 6.0. If you need help with this procedure or have any question, please contact Microsoft Technical Support.

To clear the Temporary Internet Files folder and delete cookies

NOTE: Some Web sites use cookies to allow you to log in to them. Before you delete cookies, make sure that you have a record of all such login names and passwords.

  1. Start Internet Explorer.
  2. Click Tools > Internet Options.
  3. In the Temporary Internet Files section, click the Delete Files button.
  4. Check Delete all offline content and then click OK.
  5. Click Delete Cookies and then click OK.

Antivirus Protection Dates

  • Initial Rapid Release version February 13, 2004
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version February 13, 2004
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date February 13, 2004

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

Technical Description

By embedding a specially crafted URL in a Web page and having that URL refer to a CHM file containing an HTML file with scripts in it, an attacker could force the user who views the Web page with a vulnerable version of Internet Explorer to download and execute files.


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.


This is a detection for exploits of a Microsoft Internet Explorer vulnerability, so it therefore does not need to be removed in the same manner as a virus or worm.

It is important that you apply the patch for the vulnerability as described in Microsoft Security Bulletin MS04-013 . Once patched, the system is no longer be vulnerable to the exploit.

If the exploit has run on your system, it is possible that some HTML files remain on the infected computer, even after the system was patched against the vulnerability.

The most likely place to find such files are the Internet Explorer Temporary Internet Files and cookies. If you are still getting detections after applying the patch, the files should be deleted. See the Additional Information section for instructions.

Writeup By: Frederic Perriot