Iptables

mostra o que está na tabela do iptables

iptables -L -n

bloqueando IP por uma hora

#!/bin/bash
iptables -I INPUT -s $1 -j DROP
at ${2:-now+1hour} <<<"iptables -D INPUT -s $1 -j DROP"

Save it as /usr/local/sbin/blockip and run blockip 1.2.3.4 or blockip 1.2.3.4 now+2hours. By default the IP is blocked for 1 hour.

You can replace DROP with REJECT if you prefer REJECT semantics.

referência

• http://superuser.com/questions/933152/program-to-block-an-ip-temporarily-with-iptables