iptables only allow web traffic. Stored in /etc/iptables.rules iptables-restore < /etc/iptables.downrules sudo sh -c "iptables-save -c > /etc/iptables.rules"

Only allow basic traffic

# Generated by iptables-save v1.4.12 on Fri Jan  4 21:46:44 2013
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [247:293129]
-A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -s 127.0.0.1/32 -p tcp -j ACCEPT
-A INPUT -j DROP
COMMIT
# Completed on Fri Jan  4 21:46:44 2013