iptablesrocks.org - Deploying the firewall
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The iptablesrocks.org iptables firewall setup guide
Deploying the firewall:
Well, it's finally time to create the main firewall ruleset script. We will simply create an importable iptables ruleset script and then import it into the
iptables ruleset on your server. As soon as we import it, it instantly becomes active. So let's get started.
Create the firewall script...
vi /root/primary_firewall
#The NAT portion of the ruleset. Used for Network Address Transalation.
#Usually not needed on a typical web server, but it's there if you need it.
*nat
:PREROUTING ACCEPT [127173:7033011]
:POSTROUTING ACCEPT [31583:2332178]
:OUTPUT ACCEPT [32021:2375633]
COMMIT
#The Mangle portion of the ruleset. Here is where unwanted packet types get dropped.
#This helps in making port scans against your server a bit more time consuming and difficult, but not impossible.
*mangle
:PREROUTING ACCEPT [444:43563]
:INPUT ACCEPT [444:43563]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [402:144198]
:POSTROUTING ACCEPT [402:144198]
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
COMMIT
#The FILTER section of the ruleset is where we initially drop all packets and then selectively open certain ports.
#We will also enable logging of all dropped requests.
*filter
:INPUT DROP [1:242]
:FORWARD DROP [0:0]
:OUTPUT DROP [0:0]
:LOG_DROP - [0:0]
:LOG_ACCEPT - [0:0]
:icmp_packets - [0:0]
#First, we cover the INPUT rules, or the rules for incoming requests.
#Note how at the end we log any incoming packets that are not accepted.
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p tcp -m tcp --dport 20 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 21 -j ACCEPT
http://www.iptablesrocks.org/guide/ruleset.php (1 of 4) [2/13/2004 8:04:54 PM]
