Firewall

[Martin Lorentzson]

I'm using a simple iptables script that will block all incoming
traffic that didn't originated locally.  I've got a single ethernet
card named eth0:

  $  cat /etc/network/if-pre-up.d/iptables
  #!/bin/sh
  test "$IFACE"="eth0"  || exit
  
  IPTABLES=/sbin/iptables
  
  $IPTABLES -F OUTPUT
  $IPTABLES -F FORWARD
  $IPTABLES -F INPUT
  
  $IPTABLES -P OUTPUT ACCEPT
  $IPTABLES -P FORWARD DROP
  $IPTABLES -P INPUT DROP
  $IPTABLES -A INPUT -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
  $IPTABLES -A INPUT -s 127.0.0.1 -i lo -j ACCEPT

Just make sure that the iptables file is executable.

/Martin