# Delete all rules
/sbin/ipfwadm -I -f
# Set default policy accept
/sbin/ipfwadm -I -p accept
# unallow telnets
/sbin/ipfwadm -I -a deny -P tcp -S0.0.0.0/0 \
   -Dyour_server/32 23 -o
[ ...]
# Silently allow the packet