Neat, didn't know that! Think before I've used Traffic Control (tc) for it, but iptables would be simpler.

Available in `xtables-addons` it seems. After install:

    iptables -A INPUT -p tcp -s $SOURCE_IP -j TARPIT # add IP to tarpit
    iptables -D INPUT -p tcp -s $SOURCE_IP -j TARPIT # remove IP from tarpit