About what the first poster gives, I am not convinced of the generality of this approach. Not too practical, I am sure.
And about the Hakers News Bulletin article given by Gotsu Totsu Kotsu II above, it is still not too practical. There are systems that block access for a time after a number of failed attempts.
K.I.S.S. ===> "Keep It Simple, Stupid"
"Simplicity is the ultimate sophistication." (Leonardo da Vinci)
"Everything should be made as simple as possible, but no simpler." (Albert Einstein)