On Sat 20 August 2011 10:38:43 Grant did opine thusly: > I like the policy of blocking all ports in and out with a firewall > and only opening the ones you need. Bittorrent makes that > difficult since it connects out to unpredictable ports. Do you > block outbound ports with a firewall or only inbound?
For the most part only inbound. Blocking outbound is pretty much pointless as a security measure. You cannot control what people will want to connect to outbound. Every time you think you have a complete list, someone will come along and provide you with heaps of reasons as to why their request is legit (and it usually is!) What you can control completely is the services you offer and on what ports, therefore inbound firewalls make sense. That's not to say we don't use outbound firewalls at all, we do - as a policy measure. Outbound port 25 is blocked so that people will use my relays instead. I trust them to play nice, they trust me to keep the service up. For us, this works well. But as a security measure the entire model falls apart as soon as someone with a clue comes along. I have this game I play with our firewall/security people where I get to look smug. Tool of choice? ssh The security benefits from outbound connections to my mind are: warm-and-fuzzy security cover-your-ass security just-do-whatever-the-damn-auditor-says-so-he-can-stfu security i-don't-know-what-i'm-doing security but almost never real security. That's better done with permanent ACLs on the routers. -- alan dot mckinnon at gmail dot com
