To use sshguard you must add the following to /etc/pf.conf:

table <sshguard> persist

block in quick on egress proto tcp from <sshguard> \
	to any port ssh label "ssh bruteforce"

To start sshguard automatically at boot time, add these lines to /etc/rc.local:

if [ -x /usr/local/sbin/sshguard ]; then
	echo -n ' sshguard'
	/usr/local/sbin/sshguard -l /var/log/authlog >/dev/null 2>&1 &
fi
