MS06-050 is not categorized as virus, worm, Trojan or backdoor. It is a group of important vulnerabilities in Hyperlink Object Library in Windows 2003/XP/2000, which allows to remotely execute arbitrary code in the vulnerable computer.
If exploited successfully, MS06-050 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 sending via email a message that contains a link or an Office file that includes a link and enticing users into following it.
If you have a Windows 2003/XP/2000 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.
Additionally, bear in mind that this security bulletin replaces the previous bulletin, called MS05-015.