Someone

#!/bin/bash

  # Flush any existing rules and set the default policies
  iptables -F
  iptables -P INPUT   DROP
  iptables -P FORWARD DROP
  iptables -P OUTPUT  ACCEPT

  # Accept anything from myself
  #iptables -A INPUT -s 127.0.0.1/32 -j ACCEPT
  iptables -A INPUT -i lo -s 127.0.0.1 -d 127.0.0.1 -j ACCEPT

  # Allow myself to be a non-passive FTP client
  #iptables -A INPUT -p tcp --dport ftp-data -j ACCEPT

  # Do not allow a local user to connect to a remote Telnet
  # server and thus give away login and password information:
  iptables -A OUTPUT -p tcp --dport telnet -j REJECT

  # Steam
  iptables -A INPUT -p tcp --dport 27000:27041 -j ACCEPT
  iptables -A INPUT -p udp --dport 27000:27041 -j ACCEPT

  # Steam Friends Service
  iptables -A INPUT -p udp --dport 1200 -j ACCEPT

  # Quake 3
  iptables -A INPUT -p tcp --dport 27960 -j ACCEPT
  iptables -A INPUT -p udp --dport 27960 -j ACCEPT

  # Quake 2
  iptables -A INPUT -p udp --dport 27910 -j ACCEPT
  iptables -A INPUT -p udp --dport 27910 -j ACCEPT

  # StarCraft
  iptables -A INPUT -p tcp --dport 6112 -j ACCEPT
  iptables -A INPUT -p udp --dport 6112 -j ACCEPT

  # AIM DCC
  iptables -A INPUT -p tcp --dport 5190:5200 -j ACCEPT
  iptables -A INPUT -p udp --dport 5190:5200 -j ACCEPT

  # Custom DC++ Port
  iptables -A INPUT -p tcp --dport 27072 -j ACCEPT
  iptables -A INPUT -p udp --dport 27072 -j ACCEPT

  # If it's not one of the above allowed cases, block connection
  # attempts to privileged TCP and UDP ports.
  #
  # Silently drop unwanted packets to waste the attacker's time.
  iptables -A INPUT -p tcp --dport 1:65535 -j DROP
  iptables -A INPUT -p udp --dport 1:65535 -j DROP

  # Report what happened
  echo 'Firewall rules installed:'
  iptables -L

  exit