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Re: [Nmh-workers] Verizon DSL block
From: |
Ken Hornstein |
Subject: |
Re: [Nmh-workers] Verizon DSL block |
Date: |
Fri, 22 Jan 2010 17:12:58 -0500 |
>> The port 25 block is pretty much standard for large ISPs today; it's
>> to prevent spammers from using massive networks of compromised PCs to
>> deliver spam.
>
>Changing ports is useless unless authentication is required.
>If deterring spammers is the primary goal, then ISPs can just require
>authentication for customers over the standard SMTP port.
I'm not really here to debate you on this ... but the _point_
is to prevent zombie PCs from doing final delivery to random sites
on the internet. It's a lot easier for the ISP to notice, "Hey, you
just tried to send 5000 emails in the space of 2 minutes", if their
mail servers are in the message path. And many ISPs are doing stuff
like POP-before-SMTP instead of authentication.
>However, even with authentication, if a system is zombied, probably
>would not take much for authentication credentials to be stolen by
>the malware and used for sending out spam.
It doesn't seem like they're doing that just yet, but of course it's
a continual arms race.
--Ken
Re: [Nmh-workers] Verizon DSL block, levinedl, 2010/01/22