MS07-061 is not categorized as virus, worm, Trojan or backdoor. It is a critical vulnerability in Windows URI handling on Windows XP/2003 computers, which allows arbitrary code to be remotely executed in the vulnerable computer.
A URI (Uniform Resource Identifier) is a string of characters used to identify resources from the Internet or over a network. An example of URI are URLs.
If exploited successfully, MS07-061 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 creating a specially crafted URI and hosting it in a website or sending it in an attached file via email. An attacker would have to entice users into visiting the website or running the attachment.
The most vulnerable systems are Windows XP/2003 computers with Internet Explorer 7. However, if you have a Windows XP/2003 computer with another Internet Explorer version, it is also recommended 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 patch replaces a previous one, called MS07-045.