Stealth Blocking
Eric A. Hall
ehall at ehsco.com
Thu May 24 16:46:19 UTC 2001
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/
More information about the NANOG
mailing list