illegal access using ssh

[Amish Rughoonundon <axr0284@rit.edu>]

Hi,
I was looking at my auth.log file and I saw a bunch of these things:
Nov 28 16:22:41 localhost sshd[11363]: Illegal user nobody from 212.0.148.2

I was wondering if there is a way to filter the ip allowed to access the 
computer and allow only 1 ip (mine) to do so. Thanks a lot,
Amish