To expand on Cleo's response, you can just block out certain ip blocks in .htaccess or if you have your own box you can use iptables to just drop the packets.
Here is a snippet that I got from MrYellow of webpimps.com
Code:
Order allow,deny
allow from all
#Saudi
deny from 212.138.47.
deny from 212.138.64.
#unknown
deny from 203.149.16.
#Egypt
deny from 62.114.126.
#Chez
deny from 195.116.60.1
#UAE
deny from 195.229.241.
-A