In this episode I talk about how to build a cheap hosted Mutillidae server to safely hack away on while keeping other Internet prowlers out. Here are the basic commands to run to lock down the Digital Ocean droplet's iptables firewall:

*Flush existing rules*

**sudo iptables -F**

*Allow all concurrent connections*

**sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT**

*Allow specific IPs/hosts to access port 80*

**sudo iptables -A INPUT -p tcp -s F.Q.D.N --dport 80 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT**

*Allow specific IPs/hosts to access port 22*

**sudo iptables -A INPUT -p tcp -s F.Q.D.N --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT**

*Block all other traffic:*

**sudo iptables -P INPUT DROP**

*Provide the VPS loopback access:*

**sudo iptables -I INPUT 1 -i lo -j ACCEPT**

*Install iptables-persistent to ensure rules survive a reboot:*

**sudo apt-get install iptables-persistent**

*Start iptables-persistent service*

**sudo service iptables-persistent start**

*If you make iptables changes after this and they don't seem to stick, do this:*

**sudo iptables-save > /etc/iptables/rules.v4**

See this Digital Ocean article for more information.