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more on Verizon Discovers The Cost Of Being Too Aggressive In Blocking Spam]
From: David Farber <dave () farber net>
Date: Tue, 4 Apr 2006 15:07:41 -0400



Begin forwarded message:

From: Lee Revell <rlrevell () joe-job com>
Date: April 3, 2006 7:01:21 PM EDT
To: dave () farber net
Cc: ip () v2 listbox com, cbeck () pacanukeha net
Subject: Re: [IP] Verizon Discovers The Cost Of Being Too Aggressive In Blocking Spam]

(please remove my name)

On Mon, 2006-04-03 at 18:13 -0400, David Farber wrote:

Begin forwarded message:

From: Chris Beck <cbeck () pacanukeha net>
Date: April 3, 2006 6:04:12 PM EDT
To: Dave Farber <dave () farber net>
Subject: [Fwd: Verizon Discovers The Cost Of Being Too Aggressive In
Blocking Spam]

Hi Dave,

I didn't see this fly by on IP -

"In late 2004 Verizon implemented a massive blocklist for DSL
customers, that seemed to block a ton of email from outside the
country -- with no way to get around the list.

What a terrible precedent.  No good deed goes unpunished.

This kind of thing was commonplace and necessary before spam filtering
became sophisticated.  When I worked at an ISP I had to block wanadoo.fr
once (this generated one complaint out of thousands of users, and
blocked thousands of spam mails per day).  At one point before I started
Russia was briefly blocked (for hacking/bot attacks not spam).  Before
we bought a dedicated spam filtering appliance our sendmail files
contained hundreds of networks and domains, mail from which was bounced
with a "Spammers go away" message.  Domain based filtering later became
ineffective once spammers started buying throwaway domains.

You have to understand that when an ISP is under spam attack, it often
comes down to a choice between heavy handed blocking, and having the
mail servers fall over, at which point remote systems may start to
bounce mail or even silently discard it (the volume of spam having made
queueing or even bouncing impractical for many hosts).  Probably 25 to
50% of tech support resources were already wasted responding to spam
complaints from users.  It was a very common reason for users to cancel.

While false positives are a problem, insufficiently aggressive spam
filtering can also cause mail to be lost, as they won't be able to pick
the legit mails out of the hundreds of spam messages.

In this day and age if an ISP doesn't aggressively filter spam, they
soon won't have any users left.

I don't quite buy that there was absolutely no way to get around the
list.  It seems more likely that these users were sending mail from
systems or networks that were still spewing spam, and the blocks were
not fine grained enough.  It makes no sense that Verizon would refuse to
de-list an innocent system.




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