iptables -F
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT
iptables -A INPUT -j DROP
iptables -A INPUT -p udp --dport 67:68 -j ACCEPT
iptables -A INPUT -p tcp --dport 67:68 -j ACCEPT
iptables -A INPUT -p udp --dport 53 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT

Add ACCEPT rules to your firewall configuration script to re-enable access to
•   DHCP (UDP and TCP ports 67 and possibly 68?) Be able to explain which ports you blocked.
•    DNS (UDP port 53)
•   HTTPD (TCP port 80)
•   Ping (ICMP not UDP or TCP!) services from our network only!  Use CIDR mask notation.
Use the iptables man page as a reference for writing your new rules
Save and re-apply your rules.
Confirm the network services are now available again by re-running ping and refreshing/reloading your QTWeb browser page on WINPE2.