Resources about building a firewall in Linux -- can be done just using a script.

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Contents

Notes

Civileme says (Re: [newbie] good linux firewall?; 23 Jul 2002):

Mandrake has a wonderful standalone firewall called SNF, but it requires a dedicated machine to stand between the internet interface and the local network running nothing but SNF. This sort of "border firewall" is also available as "smoothwal", a separate product, and esmith gateway, and probably as the linux Router Project in one of its many forms.

If you want a firewall on your own machine, open a terminal and

su

to get into privileged mode then

Inter7lt;tab>

will cause InteractiveBastille to be spelled out

and <return> will run it and you can learn about firewalling as you choose your rules to set it up.

You may want to edit /etc/security/limits.conf to keep from being gigged about files too big. It has a rather low limit, which is activated by setting up the firewall.

Resources

Example Firewall Scripts

• http://www.linuxguruz.org/iptables
• http://www.linuxguruz.org/iptables/scripts/rc.firewall_023.txt
• http://linux-sxs.org

Tutorials

• Civileme recommends running InteractiveBastille (su'd to root) to set up your firewall and learn about it at the same time.
• Iptables Tutorial 1.1.9; Oskar Andreasson; 2001 -- recommended by daRcmaTTeR

Notes

from Rob Gillen:

BTW, if you are running a simple in-house network where you aren't overly concerned about internal attacks, you could just allow all local TCP packets through your firewall. You probably will want to block all connections to X (port 6000) from the external world though. Something like this will allow everything on your LAN to pass through the firewall.

  INTIF=eth1                                # network interface connected to your LAN
  INTNET=192.168.1.0               # network associated with your LAN
  /sbin/iptables -A INPUT -i $INTIF -s $INTNET -j ACCEPT
  /sbin/iptables -A INPUT -s $INTNET -j DROP        # dump anything else claiming to be on LAN

Testing Your Firewall

Some sites to help you test your firewall:

• http://www.dslreports.com/tools
• http://crypto.yashy.com/nmap.php
• https://secure1.securityspace.com/smysecure/norisk_index.html
• http://grc.com/ -- Shields Up

Recommended by Others

• http://www.linuxnewbie.org/nhf/Networks/Firewall_Installation.html
• http://www.simonzone.com/software/guarddog/
• http://www.simonzone.com/software/guarddog/manual2/
• floppyfw

Contributors

• RandyKramer - 18 Apr 2002
• <If you edit this page, add your name here, move this to the next line>

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