How do I stop bruteforce SSH login attempt?

[Soo-Hyun Choi]

Hi,

A few days ago, I have noticed that my system is under constant
attack(?) with a bruteforce SSH login - e.g., from a single IP
address, it tries like 100 ~ 200 ssh login trial with all different
user names, and go away.

I know how to block it in a FreeBSD system with "denyhost" or
"bruteforceblocker" from the ports, but I have little knowledge in my
Ubuntu 5.10 box.

Would there be anyone who could tell me something about it?

Thank you.
Soo-Hyun