Base policy :

 iptables -P INPUT DROP
 iptables -P OUTPUT DROP
 iptables -P FORWARD DROP

Logging issues :

 iptables -N LOG_DROP
 iptables -A LOG_DROP -j LOG --log-prefix '[IPTABLES DROP] : '
 iptables -A LOG_DROP -j DROP


 iptables -A FORWARD -j LOG_DROP
 iptables -A INPUT -j LOG_DROP
 iptables -A OUTPUT -j LOG_DROP 


For the lo Interface 

 iptables -A INPUT -i lo -j ACCEPT
 iptables -A OUTPUT -o lo -j ACCEPT 


For DNS : 

 iptables -A INPUT -i ppp0 --protocol udp --source-port 53 -j ACCEPT
 iptables -A OUTPUT -o ppp0 --protocol udp --destination-port 53 -j ACCEPT
 iptables -A INPUT -i ppp0 --protocol tcp --source-port 53 -j ACCEPT
 iptables -A OUTPUT -o ppp0 --protocol tcp --destination-port 53 -j ACCEPT 


To access web :
 iptables -A INPUT -i ppp0 --protocol tcp --source-port 80 -m state --state ESTABLISHED -j LOG_ACCEPT
 iptables -A OUTPUT -o ppp0 --protocol tcp --destination-port 80 -m state --state NEW,ESTABLISHED -j LOG_ACCEPT