[129385] in North American Network Operators' Group
RE: ISP port blocking practice
daemon@ATHENA.MIT.EDU (Paul Stewart)
Fri Sep 3 18:22:50 2010
Date: Fri, 3 Sep 2010 18:22:33 -0400
In-Reply-To: <alpine.BSF.2.00.1009040017320.83347@joyce.lan>
From: "Paul Stewart" <pstewart@nexicomgroup.net>
To: "John R. Levine" <johnl@iecc.com>,
"Owen DeLong" <owen@delong.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
It's extremely effective for us (not a large provider by any means). We
block outbound 25 on all dynamic IP customers - to date it's never been
a problem for our customers. Customer's who have static assignments are
not blocked by default.
Paul
-----Original Message-----
From: John R. Levine [mailto:johnl@iecc.com]=20
Sent: Friday, September 03, 2010 3:20 PM
To: Owen DeLong
Cc: nanog@nanog.org
Subject: Re: ISP port blocking practice
>> It's been extremely effective in blocking spam sent by spambots on
>> large ISPs. It's not a magic anti-spam bullet. (If you know one,
>> please let us know.)
>>
> That simply hasn't been my experience. I still get lots of spam from
booted hosts in large provider networks, and yes, that includes many
that block 25. As near as I can tell, 25 blocking is not affecting
spammers at all, just legitimate users.
I know people at large ISPs with actual data. Port 25 blocking is quite
effective.
R's,
John
