services to block for a firewallsetup

There are generally two schools of thought when it comes to setting up a firewall:
1. Everything allowed unless expressly denied.
2. Nothing allowed unless expressly permitted.

My recommendation to you (as well as what I have implemented here) is to use thought #2. Don't worry about what you want to deny, shut everything down and open up only what you need to. This will help to keep you covered, otherwise every time someone comes up with a new hack, trojan, back-door, etc... you 'll haveto make updates. There are litterally thousands of ports that are used by various Trojan horse and Back door programs. do you want to have to block each one manually?

Block it all, open only the ports you need to the servers that need them, Port 80 for HTTP, 25 SMTP, 21 FTP, etc... if you have special applications that use specific ports code it into the firewall for that server only, protects the rest from a possible hack.

good luck with it,
-Mike

Block everything.

You don't say what version you're running, but after you're done, portscan the machine from a box outside the forewall, and make sure you see nothing.

IPFWADMN or IPChains will open the ports for you when people inside the Lan need out onto the internet. And either of these programs will also close the ports again after the person is finished using them, so that no holes remain.

Any access to that server is dangerous. ANY.

The firewall can be set up so that it isdead to the outside world, and still allows seamless access for internal users going out to the internet.

Kev.

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