firewall question

I have just loaded linux ubuntu along side windows and my question is firewall related.I have set up a firewall for linux ubuntu and left my windows firewall active in case I revert back to it…can there be a conflict between the linux firewall and windows commercial firewall,or is there no link between the two other than you can boot either at start up.

If you are talking about the firewalls on the same machine, then NO, there can be no conflict, as nothing is being run from the non-booted OS… so only one firewall is active at any given time.

And before anyone asks… yes, this still applies to a Wubi installation… even after a Wubi installation Windows never gets booted, as you choose the OS to boot from the Windows bootloader.
(The Windows firewall can however get in the way of the actual Wubi installation process as this is initially being run from within Windows, and Wubi needs to download the Ubuntu ISO image… but after the initial installation you boot either Windows or Ubuntu)

If you mean can a Linux firewall conflict on a network with the firewall on a Windows machine, then YES… well in truth it isn’t really a conflict as such, but both firewalls would need rules to allow communication of whatever you wanted to allow through.

Although unless you are running a server, I can’t really see the need for running a firewall in Linux (specially if you are connecting to the web through a router with NAT).

If you are running your Linux box behind a NAT router (which you should be, slap yourself if you’re using a modem / dongle) then you really don’t need a firewall … unless you are using some sort of mechanism to allow remote access to your box. (OpenVPN or such like)

Reasoning: the NAT router is by default a firewall which will not allow incoming connections.
(i.e. it blocks all incoming connections by default so there’s nothing left for your firewall to do)

There is a caveat; large organisations who have uncontrollable staff often limit “outgoing” connections, for example they might ban access to facebook or twitter … if you find you want to stop yourself from accessing certain services, you may want to install a firewall for this purpose. (or indeed if you are sensitive about applications you have installed from accessing certain services)

If you do want a firewall and like pretty Windows, then take a look at http://www.fs-security.com/

I tend to use http://firehol.sourceforge.net/ , simply because I’ve not found anything as flexible / better.
(this is ideal for servers although it works just as well on GUI workstations, but it’s ‘command-line’ only)