I have my Linux box connected directly to the 'Net. I have a Win XP box behind it using a 192.68 ip address. The Linux box has firewall and when I run GRC to proble my ports in Win XP, only shows port 22 open, which is fine. No other ports are opened...My question is, do I need to continue to run a Firewall on the XP box? Seems to me its not needed...
thxs
dareino

If its a software firewall, maybe, as Windows can get trojans, which will not be noticed by the Linux machine ( afterall it might think it can trust the stuff coming in on the Local network. ) not all trojans use odd ports that you can tell linux just to block from the windows machine.

leonscape
so your saying the windows box could become infected (infected email, file etc)? Then if the windows box had all ports merrily open the trojan could easily spread to the linux box... OR to any other windows box you might have behind the linux box. Hmm I've never thought of that before

It won't infect the Linux box, but it could probably infect other windows machines, or get back out to the rest of the internet.

sorry yeah, guess there aren't any trojans written so well as to infect both windows and linux

Or in fact there are no trojans currently for Linux. There incredible difficult to write. I mean how do you damage, or watch, or infect a machine that won't install your tojan without root permission?

Your machine has to be hacked to do it, you have to get in, then you need a security hole in the machine to get root from there, and most linux machines by default don't allow remote logins, so even that vector won't work most of the time.

Where with windows, you just need a click in a browser, or a malicious activeX component, or an e-mail. Thats a world of diffrence.

You might be thinking of the term trojan in some other way, but there have been a number of linux trojans:

http://www.cert.org/advisories/CA-1999-02.html

There have also been cross-platform viruses that affect both windows and linux systems:

http://securityresponse.symantec.com...ux.simile.html

However they are extrememly rare. But taking precautions against viruses from the inside does have its place. A notorious example of this is a group of windows clients that have samba shares. Often when these windows systems are infect they will try to spread viral code via the samba share. Another good example would be a smtp server.