North American Network Operators Group

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RE: SMTP relaying policies for Commercial ISP customers...?

  • From: Daniel Reed
  • Date: Fri Feb 13 18:08:55 2004

On 2004-02-13T15:30-0600, Ejay Hire wrote:
) You could use AOL's tactic and transparent proxy all
) outbound port 25 traffic.  Then it'd  be a relatively simple
) matter to add mr. spammer's ip to a hosts.deny.  If you were

You may also need to filter inbound packets with a source port of 25, or any
other ports you capture.

As I believe has been mentioned here before, some spammers may use a dialup
account just for its IP address, collecting return packets on the dialup
interface but sending the actual content through some higher-bandwidth,
unfiltered pipe. Filtering what goes out over the dialup account would be
largely ineffective in this case, as nothing actually needs to be sent
through that interface for the transmissions to succeed.

Daniel Reed <[email protected]>
"True nobility lies not in being superior to another man, but in being
superior to one's previous self."