Linux Firewalls Post: 7766

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Top Forums UNIX for Advanced & Expert Users Linux Firewalls Post 7766 by loadc on Monday 1st of October 2001 10:54:46 PM

10-01-2001

Registered User

Just a note...

If you have some time, ANtiOnline put out an article the other day,

PIX has an issue with SMTP traffic, it will allow trafiic through and may allow for compromise on mis-configured or older SMTP setups. There is no workaround nor any fix, Cisco is suggesting using another way of securing your smtp server.

Sorry for what seems like a bit of a dig, it's not meant as such,
I agree with the previous poster, if it ain't broke, don;t fix it, but if you really want to change, keep in mind:
Linux ( as of ipchains, not sure with iptables) is a fast firewall, it reads from teh bottom up on the rules file and the first match counts. This makes for fast processing.

BSD, uses berkeley packet filter and reads from the top down with a last match counts ideal. this is slower, but it is much more thorough. that packet will pass through every rule applicable to itself and see what matches and what doesn't. the read is also from the top down, this is a much more understandable format to write rules in (for most, anyway).
It somes to what you want to be saddled with, and which one can you config better/recover faster? Assuming this is your firewall, I am also assuming that you'll want to run SNort or something equally useful inside. A firewall is only a barrier, an IDS is a tool.

Now, if I could go religious on you for a minute...

I've heard from many of the Linux advocates that I work with that "standardizing on one operating system is EXACTLY what is wrong with the Windows approach, that is why they champion Open Source and Linux. Why then, does EVERY ONE of them want EVERYONE to run EVERYTHING on Linux?!?! Isn't that really the same crap in a different pile? I'm not down on Linux, and I don't hate Microsoft, they have done some things I think are fine, but I really think that some of the zealots I work with (I'm not inclusive, I'm only ranting about the ones I know) ought ot take a look at what they are saying and compare it to the Microsoft literature. They might be surprised at how alike they sound in some respects.

I'll get down now,

loadc

loadc

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LEARN ABOUT DEBIAN

network.conf

NETSCRIPT-2.2.conf(5)						File Formats Manual					     NETSCRIPT-2.2.conf(5)

NAME

       /etc/netscript/network.conf - interface, firewalling, and QoS configuration file.

       /etc/netscript/if.conf - interface setup shell script file

       /etc/netscript/qos.conf - QoS setup shell script file

       /etc/netscript/ipfilter.conf - IP chains filtering shell script file

       /etc/netscript/srvfilter.conf - server IP filter shell script file

DESCRIPTION

       This manpage is a place holder until something better is written when the netscript itself has stopped changing rapidly.

       Please  see  the README file in the /etc/netscript directory, and READ the configuration files if you need to change them.  Apart from net-
       work.conf, all of them contain sh (1) shell script functions which are there so that various things can be altered  or  hooked  in  at  the
       right place. Network.conf contains the full network setup details, including special interface setup for the likes of ciped/pppd/wanconfig,
       and is fully commented with examples given.

UPGRADE PATH FROM KERNEL 2.2.X
       The firewall/IP filtering stuff in ipfilter.conf is the part that changed radically with the move to iptables and a far better way of  set-
       ting  up  the  IP filtering rules, however the QoS and interface startup/shutdown in if.conf have changed but are backwards compatible with
       the old 2.2.x ipchains version of netscript for the interface address configuration settings.  You will have to set up the filtering  again
       to use iptables by directly using the iptables commands.

       Also,  the  kernel  2.2.x version scripts are set up so that iptables is only run on a 2.4.x kernel, otherwise IP forwarding is disabled if
       beforehand you set IPFWDING_KERNEL to FILTER_ON in network.conf.

       This means that when you upgrade a box to a 2.4.x router kernel, you should then be able to reboot it and log  into  remotely  and  upgrade
       netscript  to  the version that will support 2.4.x.  In this situation, if you have set old IPFWDING_KERNEL setting to FILTER_ON beforehand
       in network.conf, all IP forwarding through the box will also be disabled.  This means that you can safely remotely upgrade a firewall.

SEE ALSO

       netscript(8), ipchains(8), iproute(8), brcfg(8).

AUTHOR

       This manual page was written by Matthew Grant <grantma@anathoth.gen.nz>, for the Debian GNU/Linux system (but may be used by others).

BUGS

       The author is lazy.  He needs to write btter man pages...

								 November 23, 2000					     NETSCRIPT-2.2.conf(5)