Re: Stealth Blocking

["Eric A. Hall" <ehall () ehsco com>]

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/