how to stop someone keep trying login to my Win2K?

From: Isabella (anonymous_at_discussions.microsoft.com)
Date: 11/17/03 

Date: Sun, 16 Nov 2003 23:51:13 -0800

>From event viewer, I find many many record show that someone try to FTP my Win2K with bad password. He continuous to try that I am sure these actions are not from my real users. Am I being hacked? How can I trace the hacker and stop him? Thanks!