Comcast's been port 25 blocking since 2004

[David Farber <dave () farber net>]

________________________________________
From: Suresh Ramasubramanian [suresh () hserus net]
Sent: Friday, January 18, 2008 12:12 AM
To: David Farber
Subject: Comcast's been port 25 blocking since 2004

Selectively at least (on a per account basis, based on high volumes)

http://news.zdnet.com/2100-3513_22-5230615.html  - Jun 10 2004

--quote--

Comcast, the nation's largest broadband Internet service, this week began
selectively blocking a network loophole commonly exploited by spammers.

The cable giant, whose broadband Internet service has more than 5.7 million
subscribers, said it will block what's known as "port 25" for accounts
suspected of sending mass amounts of unsolicited e-mail. The company will
implement blocks based on subscriber accounts with the most outbound
activity.

--end quote--

Around the same time, Declan quoted this unusually candid Comcast engineer -
http://www.news.com/2010-1034-5218178.html

--quote--

"We're the biggest spammer on the Internet," network engineer Sean Lutner
said at a meeting of an antispam working group in Washington, D.C., last
week.

Lutner said Comcast users send out about 800 million messages a day, but a
mere 100 million flow through the company's official servers. Almost all of
the remaining 700 million represent spam erupting from so-called zombie
computers--a breathtaking figure that adds up to six or seven spam-o-grams
for each American family every day.

--end quote--

Both fairly typical figures for large broadband networks where there's no
such filtering. You'll find several hundred zombie generated spam / emailed
malware etc sent out for every single legitimate email sent by a human using
that network

And that was in 2004. The zombie / virus problem has if anything become far
worse, by orders of magnitude. So if someone isn't already filtering port 25
now is the time to start.

And of course, keeping in mind what my good friend UOregon's Joe St.Sauver
says about port 25 blocking .. blocking port 25 and hoping the zombies will
go away is like treating lung cancer with cough syrup.  There's assorted
other nastiness (DDoS, phishing / id theft, password cracking efforts,
repositories for child porn, etc) that a zombie PC gets used for.

So detecting and taking down zombie PCs is the second part of the strategy.
Which is why several large providers are deploying "walled gardens" as
well.. where if your computer is infected and emitting malicious traffic, it
gets isolated into its own little corner of the internet from where only
windows update / AV etc sites, and the ISP's support page are accessible.
Users can click a button the first few times to remove themselves from the
walled garden after cleaning their PC, after which they need to call the
ISP's 1-800 number.

MAAWG best practice on walled gardens -
www.maawg.org/about/whitepapers/MAAWG_Walled_Garden_BP_2007-09.pdf

And as a complement to this, there's the IAB workshop on unwanted traffic,
held a couple of years back .. the proceedings from which were summarized in
RFC 4948.

http://www1.ietf.org/mail-archive/web/ietf-announce/current/msg03989.html

Proceedings from the workshop (dated March 2006) -
http://www.iab.org/about/workshops/unwantedtraffic/index.html

        srs

> -----Original Message-----
> From: David Farber [mailto:dave () farber net]
> Sent: Friday, January 18, 2008 9:50 AM
> To: ip
> Subject: [IP] Re: the idiots at comcast suddenly started
>
>
> ________________________________________
> From: Ed Gerck [egerck () nma com]
> Sent: Thursday, January 17, 2008 10:29 PM
> To: David Farber
> Cc: ip
> Subject: Re: [IP] the idiots at comcast suddenly started
>
> Comcast's customers have a worse problem in 2008 -- some can't get
> email.
>
> SF bay area comcast is having large, yet unsolved email problems since
> start 2008. According to the error message I saw in one such bounce
> case
> (copy available by request), email to at least some of their customers'
> comcast
> address is being blocked before reaching comcast because comcast's IP
> pool is now in spam black-lists.
>
> So, their sudden blocking of port 25 seems to be a quick, ugly
> measure to try to get their IPs off spam lists, so their clients may
> at least receive email again.
>
> Of course, other solutions exist but comcast, that was not very
> proactive
> before when the problem started even before 2007, may just stick with
> the ugly solution...until it also fails.
>
> Cheers,
> Ed Gerck
>
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