A simple iptables config script, using some tutorial's best practices.

iptables.sh

sudo iptables -A INPUT -i lo -j ACCEPT                                 # Local loopback
sudo iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT  # Established connections
sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT                     # SSH
sudo iptables -A INPUT -p tcp --dport 28600:28699 -j DROP              # Block 286XX
sudo iptables -A INPUT -j DROP                                         # Drop everything else