MS06-020 is not categorized as virus, worm, Trojan or backdoor. It is a group of critical vulnerabilities in Macromedia Flash Player on Windows XP/Me/98 computers, which allows arbitrary code to be remotely executed in the vulnerable computer.
Macromedia Flash Player is not a Microsoft product, but an Adobe one. However, this program is bundled with the versions mentioned above.
If exploited successfully, MS06-020 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.
These vulnerabilities are usually exploited by creating a specially crafted SWF file that can be sent via email or hosted in a web page.
If you have a Windows XP/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.
Bear in mind that this Microsoft bulletin is only valid for Macromedia Flash Player versions bundled with Windows XP/Me/98. If you have installed it in any other way, you should refer to Adobe official website and download the latest security update available for Flash Player.