IPTABLES IP BLOCK SCRIPT

Instalamos apt-get install iptables-persistent

#!/bin/bash
iptables -A INPUT -s $1 -j DROP
/etc/init.d/iptables-persistent save
/etc/init.d/iptables-persistent reload
#apt-get install iptables-persistent

luego probamos

root@pbx:/usr/src/asterisk-13.1.0# chmod 755 block.sh
root@pbx:/usr/src/asterisk-13.1.0# ./block.sh 195.154.174.35

Verificamos  
                                                                                                                                                                         
root@pbx:/usr/src/asterisk-13.1.0# iptables -L -n
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
DROP       all  --  195.154.174.35       0.0.0.0/0

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)