[129384] in North American Network Operators' Group
Re: ISP port blocking practice
daemon@ATHENA.MIT.EDU (John R. Levine)
Fri Sep 3 18:19:58 2010
Date: 4 Sep 2010 00:19:47 +0200
From: "John R. Levine" <johnl@iecc.com>
To: "Owen DeLong" <owen@delong.com>
In-Reply-To: <918D3F33-E46F-40F0-9325-FAE4AE5E0D05@delong.com>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
>> 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
