firewall

[m0n0]

can anyone explain me how to set up a firewall in my server Linux on a little LAN of two computers

thanks in advance

[elite_syntax]

You useing iptables or ipchins and what linux OS you useing?

[m0n0]

i´m using Mandrake 8.2

i just need to edit iptables file for a firewall
right??

[jlmb]

Im planning on setting one too.

This links from TLDP should help you:
[list=1]
http://www.tldp.org/HOWTO/Firewall-HOWTO.html
http://www.tldp.org/HOWTO/IPCHAINS-HOWTO.html
[/list=1]

[robert0380]

some basic table rules i use:

iptables -P OUTPUT DROP ### default to drop EVERYTHING
iptables -P INPUT DROP
iptables -P FORWARD DROP

#### LET ME BROWSE THE NET ####
iptables -A OUTPUT -m state --state ! INVALID -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT


if you arent running a server or any kind or a router...that is
as good as it gets in terms of being locked down,

you cant even be pinged.


if u wanna add a web server:

iptables -A INPUT -p tcp --dport 80 -j ACCEPT


and you can do this on a per-port basis for other servers as well,
if you want to access your box fron anywhere on the net you may
wanna add this:

iptables -A INPUT -p tcp --dport 22 -j ACCEPT

that allows you to ssh in, DO NOT RUN A TELNET SERVER ON YOUR
MACHINE.

[m0n0]

i´m getting this error:

init_module: Device or resource busy
Hint: insmod errors can be caused by incorrect module parameters, including invalid IO or IRQ parameters
modprobe: insmod /lib/modules/2.4.18-6mdk/kernel/net/ipv4/netfilter/ip_tables.o.gz failed
modprobe: insmod ip_tables failed
iptables v1.2.5: can´t initialize iptables table ´filter´: iptables who? (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

what can i do?
i know i need to upgrade
but how??