On Wed, 21 Aug 2002 15:55:41 EDT, Jared Mauch said:
There is an important need to perform callback but allow for the ability to protect information from possible spammers for harvesting/verificiation.
eg:
220 welcome, but no spam ehlo spammer 250-callback-secure 250 help mail from:<spammer@hotmail.com> callback=spammer.example.com 250 ok rcpt to:<jared@nether.net> 451 try again, pending callback
OK.. So now *you* have to callback and pick up the spammer's mail. What did that gain you?
there's also the need to do some sort of pki to allow callback to be secure. eg: the dns record for nether.net should have some public-key in it and then some other stuff like possibly
Much easier would be to use the existing STARTLS stuff and use the cert presented to decide if you want to accept the mail.
mail from:<realuser@hotmail.com> callback=validate.hotmail.com;key=<alkjsdfj> then pass the 'key' through the public-key availble via dns to provide back an authentication system to allow for more secure callback.
Note that the concept of a "callback" doesn't mean the same things on an IP network as it did on a POTS network. Not that callback on the POTS network was ever as secure as people thought, anyhow...
but this can still be abused depending...
Well, given that the spammer is given the opportunity to specify where to call back *TO*, you're not buying yourself anything- of COURSE the spammer is going to point you at a system where they control the horizontal and vertical. The only callback systems that ever came anywhere near working on the POTS network were ones that you told the callback "this is Fred. Call me back at the home number you've been configured with", and it called you at Fred's previously-configured phone number. Having it say 'This is Fred, call me back at 127.0.4.5' doesnt do anything for security if you're just going to call 127.0.4.5. -- Valdis Kletnieks Computer Systems Senior Engineer Virginia Tech