I have used quicktables to generate this iptables script.

Please can someone indicate as to why kazaa is not working.
My external interface is ppp0 and the internal ip is 192.168.1.10
on which kazaa is to be run through nat.

Thanks

#!/bin/sh
#
# generated by ./quicktables-2.3 on 2004.05.08.22
#

# set a few variables
echo ""
echo " setting global variables"
echo ""
export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
iptables="/sbin/iptables"

# adjust /proc
echo " applying general security settings to /proc filesystem"
echo ""
if [ -e /proc/sys/net/ipv4/tcp_syncookies ]; then echo 1 > /proc/sys/net/ipv4/tcp_syncookies; fi
if [ -e /proc/sys/net/ipv4/conf/all/rp_filter ]; then echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter; fi
if [ -e /proc/sys/net/ipv4/ip_forward ]; then echo 1 > /proc/sys/net/ipv4/ip_forward; fi

# load some modules
if [ -e /lib/modules/`uname -r`/kernel/net/ipv4/netfilter/ip_conntrack_ftp.o ]; then modprobe ip_conntrack_ftp; fi
if [ -e /lib/modules/`uname -r`/kernel/net/ipv4/netfilter/ip_nat_ftp.o ]; then modprobe ip_nat_ftp; fi

# flush any existing chains and set default policies
$iptables -F INPUT
$iptables -F OUTPUT
$iptables -P INPUT DROP
$iptables -P OUTPUT ACCEPT

# setup nat
echo " applying nat rules"
echo ""
$iptables -F FORWARD
$iptables -F -t nat
$iptables -P FORWARD DROP
$iptables -A FORWARD -i eth0 -j ACCEPT
$iptables -A INPUT -i eth0 -j ACCEPT
$iptables -A OUTPUT -o eth0 -j ACCEPT
$iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
$iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE

# allow all packets on the loopback interface
$iptables -A INPUT -i lo -j ACCEPT
$iptables -A OUTPUT -o lo -j ACCEPT

# allow established and related packets back in
$iptables -A INPUT -i ppp0 -m state --state ESTABLISHED,RELATED -j ACCEPT

# blocking reserved private networks incoming from the internet
echo " applying incoming internet blocking of reserved private networks"
echo ""
$iptables -I INPUT -i ppp0 -s 10.0.0.0/8 -j DROP
$iptables -I INPUT -i ppp0 -s 172.16.0.0/12 -j DROP
$iptables -I INPUT -i ppp0 -s 192.168.0.0/16 -j DROP
$iptables -I INPUT -i ppp0 -s 127.0.0.0/8 -j DROP
$iptables -I FORWARD -i ppp0 -s 10.0.0.0/8 -j DROP
$iptables -I FORWARD -i ppp0 -s 172.16.0.0/12 -j DROP
$iptables -I FORWARD -i ppp0 -s 192.168.0.0/16 -j DROP
$iptables -I FORWARD -i ppp0 -s 127.0.0.0/8 -j DROP

# icmp
echo " applying icmp rules"
echo ""
$iptables -A OUTPUT -p icmp -m state --state NEW -j ACCEPT
$iptables -A INPUT -p icmp -m state --state ESTABLISHED,RELATED -j ACCEPT
$iptables -A INPUT -p icmp --icmp-type echo-request -i ppp0 -j DROP

# apply icmp type match blocking
echo " applying icmp type match blocking"
echo ""
$iptables -I INPUT -p icmp --icmp-type redirect -j DROP
$iptables -I INPUT -p icmp --icmp-type router-advertisement -j DROP
$iptables -I INPUT -p icmp --icmp-type router-solicitation -j DROP
$iptables -I INPUT -p icmp --icmp-type address-mask-request -j DROP
$iptables -I INPUT -p icmp --icmp-type address-mask-reply -j DROP

# open ports to the firewal
echo " applying the open port(s) to the firewall rules from internal"
echo ""

##Allow incoming TCP port 8888 proxy traffic from internal
$iptables -A INPUT -p tcp -s 192.168.1.10 --dport 8888 -j ACCEPT


# open and forward ports to the internal machine(s)
echo " applying port forwarding rules"
echo ""


#KAZAA
$iptables -A FORWARD -i ppp0 -p tcp --dport 1450 -j ACCEPT
$iptables -t nat -A PREROUTING -i ppp0 -p tcp --dport 1450 -j DNAT --to-destination 192.168.1.10:1450


# logging
echo " applying logging rules"
echo ""
$iptables -A INPUT -i ppp0 -p tcp -m limit --limit 1/s --dport 0:65535 -j LOG --log-prefix "tcp connection: "
$iptables -A INPUT -i ppp0 -p udp -m limit --limit 1/s --dport 0:65535 -j LOG --log-prefix "udp connection: "

# drop all other packets
echo " applying default drop policies"
echo ""
$iptables -A INPUT -i ppp0 -p tcp --dport 0:65535 -j DROP
$iptables -A INPUT -i ppp0 -p udp --dport 0:65535 -j DROP

echo "### quicktables is loaded ###"
echo ""

Your rules look alright, but are you sure that Kazaa uses port 1450? The Kazaa website and all the port lists that I use all say Kazaa uses port 1214 tcp and udp (you are also only allowing the tcp traffic through).

Yes kazaa does work with these rules. I forget to set the default gateway on the windows computer.

The worrying thing is that kazaa can connect even when I comment out the kazaa specific rule and reload the script.

can you see how this can happen?

thanks

Your rules are setup to allow all outbound traffic and all inbound traffic that is related or established. So the Kazaa clients can initiate connections outbound and then inbound dowload traffic is allowed into the LAN because it is related to the clients initial outbound connection (it's now part of an established connection). Because the traffic matches the established related rule, it never reaches the rule that specifically allows kazaa (port 1450). I would guess that is why it works even though the rule is using the wrong port number. If you wish to block it, you'd have to specifically add a rule above the RELATED,ESTABLISHED rule to block the traffic.