MS04-040 is not categorized as virus, worm, Trojan or backdoor. It is a vulnerability in Internet Explorer v6.0 running on Windows XP/2000/NT/Me/98 computers, which allows to remotely execute arbitrary code in the vulnerable computer.
If exploited successfully, MS04-040 allows hackers to gain remote control of the affected computer with the same privileges as the logged-on user. If this user had administrator rights, the hacker could take complete control of the system: create, modify or delete files, install programs, create new user accounts, etc.
MS04-040 is exploited by creating a specially crafted web page, and enticing users into accessing it. An e-mail in HTML format could also be used.
This vulnerability is also used by some malware, such as the worms Bofra.B and Bofra.C, in order to affect vulnerable computers.
If you use Internet Explorer v6.0 on a Windows XP/2000/NT/Me/98 computer, it is recommendable to download and apply the security patch for this vulnerability. Access the web page for downloading the patch. However, provided that this is a cumulative patch, make sure that you download the latest security patch available.
Note: Due to the Support Lifecycle of Windows operating systems, the availability of this patch for some versions may be affected. For further information, please contact Microsoft.