Script to prevent SSH attacks while allowing you to connect from dynamic IP address.

while most of the time connecting to a remote server using openvpn would be a smart choice, sometimes it's not an option. This script is for a linux behind a firewall/router. It's intended to prevent SSH attacks (by simply denying access to the SSH port) while allowing you to connect from your own dynamic DNS, that is, if you have a dynamic ip given by your ISP, otherwise you could simply use iptables.

#!/bin/bash
valor=`host yourdyndns`
OK=$?
if [ $OK -ne 0 ]; then
  exit
fi
addr=$(echo $valor |egrep "address .*" -o)
ip=$(echo $parte |egrep "[0-9\.]*" -o)

whitelist=/root/whitelist
touch ${whitelist}

exists=`cat ${whitelist} | grep "${parte2}"`

if [ $? -ne 0 ]; then
  echo $ip >$whitelist
  iptables -F   iptables -A INPUT -s $ip -j ACCEPT
  iptables -A FORWARD -s $ip -j \ ACCEPT                                                                                         
  iptables -A INPUT -p tcp --dport 22022 -j DROP                                                                                   
fi

add this to rc.local to reload iptables during bootup:

# delete whitelist

rm /root/whitelist

# run previous script

/root/bin/testso.sh