Comment by m0nty

    $ grep -c sshd /etc/hosts.deny
    1192
    $ uptime
    11:58:51 up 327 days, 21:33,  1 user,  load average: 0.13, 0.11, 0.09

I'm using DenyHosts for this, there are alternatives but this works for me.

http://denyhosts.sourceforge.net/