Hi, I have a RH 7.1 installaiton with a 2.4.17 modular kernel. My setup works fine except for when I leave my Netscape browser open I get the following error in my logs: Feb 19 20:18:27 stud kernel: New not syn:IN= OUT=eth0 SRC=12.255.195.39 DST=204.152.184.101 LEN=341 TOS=0x00 PREC=0x00 TTL=64 ID=0 PROTO=TCP SPT=35996 DPT=80 WINDOW=40544 RES=0x00 ACK PSH FIN URGP=0 It does not take long for this to fill out my logs. I have also attached the fire wall script that I go from Oskar Andressen. TIA. Trevor. #!/bin/sh # # rc.firewall - Initial SIMPLE IP Firewall test script for 2.4.x # # Author: Oskar Andreasson <[EMAIL PROTECTED]> # (c) of BoingWorld.com, use at your own risk, do whatever you please with # it as long as you don't distribute this without due credits to # BoingWorld.com # ########### # Configuration options, these will speed you up getting this script to # work with your own setup. # # your LAN's IP range and localhost IP. /24 means to only use the first 24 # bits of the 32 bit IP adress. the same as netmask 255.255.255.0 # # STATIC_IP is used by me to allow myself to do anything to myself, might # be a security risc but sometimes I want this. If you don't have a static # IP, I suggest not using this option at all for now but it's stil # enabled per default and will add some really nifty security bugs for all # those who skips reading the documentation=) LAN_IP_RANGE="192.168.1.0/24" DMZ_LAN="172.16.1.0/24" LAN_IP="192.168.1.5/32" LAN_BCAST_ADRESS="192.168.1.255/32" LOCALHOST_IP="127.0.0.1/32" STATIC_IP="xx.xxx.xxx.xxx" INET_IFACE="eth0" LAN_IFACE="eth1" LO_IFACE="lo" IPTABLES="/sbin/iptables" ######### # Load all required IPTables modules # # # Needed to initially load modules # /sbin/depmod -a # # Adds some iptables targets like LOG, REJECT and MASQUARADE. # #/sbin/modprobe ipt_LOG #/sbin/modprobe ipt_REJECT #/sbin/modprobe ipt_MASQUERADE # # Support for owner matching # #/sbin/modprobe ipt_owner # # Support for connection tracking of FTP and IRC. # #/sbin/modprobe ip_conntrack_ftp #/sbin/modprobe ip_conntrack_irc # # Enable ip_forward, this is critical since it is turned off as defaul in Linux. # #echo "1" > /proc/sys/net/ipv4/ip_forward # # Dynamic IP users: # #echo "1" > /proc/sys/net/ipv4/ip_dynaddr # # Enable simple IP Forwarding and Masquerading # #$IPTABLES -t nat -A POSTROUTING -o $INET_IFACE -j MASQUERADE $IPTABLES -t nat -A POSTROUTING -o $INET_IFACE -j SNAT --to 12.255.195.39 # # Bad TCP packets we don't want # $IPTABLES -A FORWARD -p tcp ! --syn -m state --state NEW -j LOG --log-prefix "New not syn:" $IPTABLES -A FORWARD -p tcp ! --syn -m state --state NEW -j DROP # # Accept the packets we actually want to forward # $IPTABLES -A FORWARD -i $LAN_IFACE -j ACCEPT $IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT $IPTABLES -A FORWARD -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix "IPT FORWARD packet died: " # # Set default policies for the INPUT, FORWARD and OUTPUT chains # $IPTABLES -P INPUT DROP $IPTABLES -P OUTPUT DROP $IPTABLES -P FORWARD DROP # # Create separate chains for ICMP, TCP and UDP to traverse # $IPTABLES -N icmp_packets $IPTABLES -N tcp_packets $IPTABLES -N udpincoming_packets # # The allowed chain for TCP connections # $IPTABLES -N allowed $IPTABLES -A allowed -p TCP --syn -j ACCEPT $IPTABLES -A allowed -p TCP -m state --state ESTABLISHED,RELATED -j ACCEPT $IPTABLES -A allowed -p TCP -j DROP # # ICMP rules # $IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 0 -j ACCEPT $IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 3 -j ACCEPT $IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 5 -j ACCEPT $IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 8 -j ACCEPT $IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 11 -j ACCEPT # # TCP rules # #$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 21 -j allowed $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 22 -j allowed $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 53 -j allowed $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 80 -j allowed $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 25 -j allowed $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 110 -j allowed $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 113 -j allowed $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 443 -j allowed #$IPTABLES -A tcp_packets -p TCP -s 204.127.68.11 --dport 119 -j allowed # # UDP ports # $IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 53 -j ACCEPT $IPTABLES -A udpincoming_packets -p UDP -s 0/0 --dport 53 -j ACCEPT $IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 123 -j ACCEPT $IPTABLES -A udpincoming_packets -p UDP -s 0/0 --dport 67 -j DROP $IPTABLES -A udpincoming_packets -p UDP -s 0/0 --dport 68 -j DROP #$IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 2074 -j ACCEPT #$IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 4000 -j ACCEPT # # PREROUTING chain. # # Do some checks for obviously spoofed IP's # $IPTABLES -t nat -A PREROUTING -i $INET_IFACE -s 192.168.0.0/16 -j DROP $IPTABLES -t nat -A PREROUTING -i $INET_IFACE -s 10.0.0.0/8 -j DROP $IPTABLES -t nat -A PREROUTING -i $INET_IFACE -s 172.16.0.0/12 -j DROP # # INPUT chain # # Take care of bad TCP packets that we don't want # $IPTABLES -A INPUT -p tcp ! --syn -m state --state NEW -j LOG --log-prefix "New not syn:" $IPTABLES -A INPUT -p tcp ! --syn -m state --state NEW -j DROP # # Rules for incoming packets from the internet # $IPTABLES -A INPUT -p ICMP -i $INET_IFACE -j icmp_packets $IPTABLES -A INPUT -p TCP -i $INET_IFACE -j tcp_packets $IPTABLES -A INPUT -p UDP -i $INET_IFACE -j udpincoming_packets # # Rules for special networks not part of the Internet # $IPTABLES -A INPUT -p ALL -i $LAN_IFACE -d $LAN_BCAST_ADRESS -j ACCEPT $IPTABLES -A INPUT -p ALL -i $LAN_IFACE -d $STATIC_IP -j ACCEPT $IPTABLES -A INPUT -p ALL -i $LO_IFACE -d $LOCALHOST_IP -j ACCEPT $IPTABLES -A INPUT -p ALL -i $LO_IFACE -d $LAN_IP -j ACCEPT $IPTABLES -A INPUT -p ALL -i $LO_IFACE -d $STATIC_IP -j ACCEPT $IPTABLES -A INPUT -p ALL -i $LAN_IFACE -d $LAN_IP -j ACCEPT $IPTABLES -A INPUT -p UDP -i $LAN_IFACE -s 0/0 --dport 67 -j DROP $IPTABLES -A INPUT -p ICMP -i $LAN_IFACE -s 0/0 --icmp-type 10 -j DROP # Drop the NIMDA stuff #iptables -A INPUT -p tcp -i $INET_IFACE -m string --string "cmd.exe" --dport 80 -j DROP $IPTABLES -A INPUT -p ALL -d $STATIC_IP -m state --state ESTABLISHED,RELATED -j ACCEPT $IPTABLES -A INPUT -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix "IPT INPUT packet died: " # Allow inbound traffice on port 53 #$IPTABLES -A INPUT -i $INET_IFACE -p udp --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT #$IPTABLES -A INPUT -i $INET_IFACE -p tcp --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT # # OUTPUT chain # $IPTABLES -A OUTPUT -p tcp ! --syn -m state --state NEW -j LOG --log-prefix "New not syn:" $IPTABLES -A OUTPUT -p tcp ! --syn -m state --state NEW -j DROP $IPTABLES -A OUTPUT -p ALL -s $LOCALHOST_IP -j ACCEPT $IPTABLES -A OUTPUT -p ALL -s $LAN_IP -j ACCEPT $IPTABLES -A OUTPUT -p ALL -s $DMZ_LAN -j ACCEPT $IPTABLES -A OUTPUT -p ALL -s $STATIC_IP -j ACCEPT $IPTABLES -A OUTPUT -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix "IPT OUTPUT packet died: " # Allow outbound traffice on port 53 #$IPTABLES -A OUTPUT -o $INET_IFACE -p udp --dport 53 -m state --state ESTABLISHED -j ACCEPT #$IPTABLES -A OUTPUT -o $INET_IFACE -p tcp --dport 53 -m state --state ESTABLISHED -j ACCEPT
