[ On Friday, August 25, 2000 at 08:42:33 (-0400), Shawn McMahon wrote: ]
Subject: Re: Now the idiots at ORBS are probing random dial-ups
On Wed, Aug 23, 2000 at 05:40:34PM -0700, L. Sassaman wrote:
server at all. Since there's rarely any legitimate reason for someone to be sending mail from a mail server on a dialup line, this easily blocks a large source of spam with little risk.
Businesses all across the country are going online now with DSL.
Many DSL providers use PPPoE, putting you smack in the middle of their dialup pool.
So, your information was correct as recently as a year ago, but it's out of date now.
How does that change the picture? It shouldn't be any different! Many businesses in this region used dial-up lines until connectivity costs came down. They often had their own e-mail servers, but they were still relaying through the ISP's outbound SMTP relay host. The only difficulty was with massive exploitation of multi-level relays. It took a lot of time, and a lot of different people putting pressure on ISP postmasters to make them realise that they were also suffering theft of service when their customers were forwarding spam through their mailers. Finally as a result of major relays being listed repeatedly in ORBS and other spam-server lists, most ISPs instituted various types of policies to prevent their customers (and themselves) from being relay raped. Some did the simple thing and blocked direct SMTP connections to and from their customers, forcing all e-mail to be relayed through their secured servers. Others perform regular checks of their customer IP blocks for unauthorised and insecure mail servers. Even @Home does regular scans for mail servers for this very reason! Unless static IP space is delegated directly to a customer then there's no reason to believe that any mail server running in that space is legitimate. SMTP just does not play with dynamic IPs, especially if you don't have reliable, secure, dynamic DNS updates on both the forward and reverse! -- Greg A. Woods +1 416 218-0098 VE3TCP <gwoods@acm.org> <robohack!woods> Planix, Inc. <woods@planix.com>; Secrets of the Weird <woods@weird.com>