On October 9, 2013 at 20:18 cma@cmadams.net (Chris Adams) wrote:
Once upon a time, Barry Shein <bzs@world.std.com> said:
It's very useful for blocking spammers and other miscreants -- no reason at all to accept SMTP connections from troublesome *.rev.domain.net at all, no matter what the preceding NNN-NNN-NNN-NNN is.
If you are going to block like that, just block anybody without valid reverse DNS. If you don't trust provider foo.net to police their users, why trust them to put valid and consistent xx-xx-xx-xx.dyn.foo.net reverse?
Because they do, they just do. This isn't a math proof, it's mostly social engineering. The providers aren't trying to fool anyone, in general, it's just that clients and websites get botted.
I only see a use for reverse DNS for router interfaces (for useful traceroute info) and servers (and only really SMTP servers). Most of the rest is fluff, often out-of-date, uselessly auto-generated, etc.
It's pretty amazing how much spam comes from hosts with names a lot like ns1.example.com, their name servers. Not sure why they're so easily abused but maybe it doesn't occur to them to lock down MTAs on their name servers. -- -Barry Shein The World | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: 800-THE-WRLD | Dial-Up: US, PR, Canada Software Tool & Die | Public Access Internet | SINCE 1989 *oo*