Iptables: script to block selected or specific ip addresses

#!/bin/sh
#
# ip_block.sh
#
# block ip addresses from a blacklist
#
# www.r71.nl
# 20070215
#####################################

# file with on each line an ip address you want to block
BLOCKDB="/root/block_ip_list"

IPTABLES=/sbin/iptables

# show and remove duplicate ip addresses from the block_ip_list file
echo Removing duplicate ip addresses from block_ip_list:
sort $BLOCKDB | uniq -c  |grep -v " 1 "|grep -v ^$
sort $BLOCKDB | uniq  > $BLOCKDB

IPS=$(grep -Ev "^#" $BLOCKDB)
counter=0

for i in $IPS
do
  counter=$(($counter+1))
  $IPTABLES -A INPUT -s $i -j DROP
  $IPTABLES -A OUTPUT -d $i -j DROP
done

echo
echo
echo Number of blocked IP addresses: $counter
echo Have a secure day!