MS06-004 is not categorized as virus, worm, Trojan or backdoor. It is a critical vulnerability in the Graphics Rendering Engine on Windows 2003/XP/2000/Me/98 computers, which allows arbitrary code to be remotely executed in the vulnerable computer.
If exploited successfully, MS06-004 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.
This vulnerability is usually exploited by hosting a WMF (Windows MetaFile) image in a specially crafted web page and enticing users into accessing it, or by sending via email a specially crafted message that contains a WMF image.
If you have a Windows 2003/XP/2000/Me/98 computer, it is recommendable to download and apply the security patch for this vulnerability. Click here to 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.