http://www.justjace.com/2007/09/10/s...rdpress-admin/
The best way I have found is to secure it by limiting to your ip only. This is a simple solution and you just add this
order deny,allow
allow from 123.45.67.123 # This is your IP Address
deny from all
to your wp-admin .htaccess file
What this does is tell your server to not let ANY other ip addresses but yours into the wp-admin folder. This requires an update every once and a while unless you have a static ip, but worth the extra effort.