MS08-019 is not categorized as virus, worm, Trojan or backdoor. It is a group of important vulnerabilities in Visio 2007/2003/2002, which allows arbitrary code to be remotely executed in the vulnerable computer.
If exploited successfully, MS08-019 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.
MS08-019 is exploited by sending a specially crafted Visio file via email and enticing users into opening it or by hosting a specially crafted file in a web page and entincing users into visiting it.
If you have any of the vulnerable programs installed on your computer, it is recommended to download and apply the security patch for these vulnerabilities. Click here to access the web page for downloading the patch.
Moreover, bear in mind that this bulletin replaces a previous one, called MS07-030.