[129392] in North American Network Operators' Group
Re: ISP port blocking practice
daemon@ATHENA.MIT.EDU (Owen DeLong)
Fri Sep 3 20:24:00 2010
From: Owen DeLong <owen@delong.com>
To: "John R. Levine" <johnl@iecc.com>
In-Reply-To: <alpine.BSF.2.00.1009040017320.83347@joyce.lan>
Date: Sat, 4 Sep 2010 09:50:25 +0930
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Sent from my iPad
On Sep 4, 2010, at 7:49 AM, "John R. Levine" <johnl@iecc.com> wrote:
>>> 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.)
>>>=20
>> 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.
>=20
> I know people at large ISPs with actual data. Port 25 blocking is =
quite effective.
>=20
Does the data show that blocking was effective, as in the host didn't =
detect the block and proceed around it, or, merely that lots of hosts =
try the direct approach first?
Merely tripping over the filter, even repeatedly does not in and of =
itself prove efficacy.
Owen
> R's,
> John
