MS05-046 is not categorized as virus, worm, Trojan or backdoor. It is an important vulnerability in the Client Service for Netware on Windows 2003/XP/2000 computers, which allows arbitrary code to be remotely executed in the vulnerable computer.
If exploited successfully, MS05-046 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 can be exploited by creating and sending specially crafted packets to a vulnerable system. However, in order to exploit it on Windows Server 2003, the malicious user must be authenticated. Additionally, though attacks can be launched across the Internet, a firewall could be used in order to prevent those attacks.
If you have a Windows XP computer, access the web page for downloading the security patch.
For the other vulnerable operating systems, namely Windows 2003/2000, please refer to Microsoft's security bulletin by clicking here.