blocking an ip after n failed login attempts

[David N Moore]

Hi,
        I have been poking around with google looking for some ideas
for a solution to this problem.  Can you think of an easy way to block
all connections from a certain ip if it tries log in say 5 times and
fails?  The idea being that it would stop someone from using a
dictionary-based attack if they had a user-name.

Any input would be appreciated.

-dave