On Tue, 21 Sep 2004, Douglas Otis wrote:
As a prophylactic measure, Port 25 is blocked or transparently intercepted to monitor the network via error logs. For external mail submissions, Port 587 would be recommended.
There is an overview of this at: http://www.ietf.org/internet-drafts/draft-hutzler-spamops-01.txt
We want to receive abuse email and act on them, doesn't matter if customers are infected and sending spam or if they're infected and trying to remote-exploit web-servers or windows computers or what have you. We've been considering using netflow to detect end-users doing a lot of port 25 activity towards a lot of random destinations, I find this much more net-friendly than to just block 25 and force them to use our smarthost (also stops our smarthost from being blacklisted by some overzealous blacklist-admins). Starting to block just means you will have to block more and more all the time. Port 135-139 and 445 will be practially unusable on the network for a long time (some users complain about this). I was under the impression that most blacklists would have a time-out period when there was no more activity from this certain IP, it would be removed from the blacklist. Is this not the case? Also, having hundreds of blacklists as per your email seems like a very silly idea? I can understand 3-5, but hundreds? -- Mikael Abrahamsson email: swmike@swm.pp.se