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Re: Stealth Blocking
From: "Eric A. Hall" <ehall () ehsco com>
Date: Thu, 24 May 2001 09:46:19 -0700



Returning to operational traffic:

One thing that I think *will* help, particularly in the short term, is
port 25 blocking of dialup ports.  It's my personal opinion that this
will have the greatest impact on spammers who abuse open relays.  I've
watched this happen over the last few months, as various large networks
have secured their dialup ports.  It's impressive.

TCP rate-limiting on outbound traffic to *:25 would also be extremely
effective, particularly on unclassified customer traffic, and without the
heavy-handed nature of denying all dial-up traffic. Rate-limiting doesn't
interfere with low-volume legitimate mail, but it really cramps spam.

-- 
Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/


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