[Asterisk-Users] Re: VoIP SPAM, what's next ?

[John Todd]

At 10:09 PM +0200 on 8/10/04, Soren Rathje wrote:
>John Todd wrote:
>>  At 7:14 PM +0200 on 8/10/04, Soren Rathje wrote:
>>>  Gang,
>>>
>[snip]
>>>
>>>  /Soren
>>>
>>>  It is the mark of an educated mind to be able to entertain a thought
>>>  without accepting it.
>>>  - Aristotle
>>
>
>Ok, so we moved here from *-dev, no problem... ;-)
>
>  > VOIP Spam is actually pretty trivial to take care of, if only the
>>  manufacturers would wise up.  We're in the same place we were with
>>  SMTP about twelve years ago.  I'm sure we'll see a slew of patents
>>  and chest-pounding by people with obvious or trivial solutions -
>>  welcome to the New WIPO World.
>>
>>  The solution is simple: "End devices should have the option to only
>>  accept authenticated requests."
>
>If IP Telephony is supposed to "grow up"/mature into a technology 
>that will replace TDM over time, this is not an option unless you 
>are building whitelists of gigantic proportions...
>

You're jumping to an overly broad conclusion that whitelists must be 
created to contain the whole world.   I'm saying that I don't know 
the combination that will best serve the purpose: whitelists, 
blacklists, chains of trust, PKI, whatever.  I _do_ know that if my 
phone keeps accepting calls from everyone without using _any_ method 
of authentication, that we can't even debate what method is best or 
worst, because the calls will just pour in through the unprotected 
last device in the path.

>  > That's pretty simple, but that is the key to the whole solution.
>>  However, most end devices will blindly accept any call that they're
>>  given, so long as the destination number is correct.  I've seen a few
>>  phones (Polycom is the only one that comes to mind) which will
>>  challenge INVITEs.  SIP devices are pretty smart, but I don't think
>>  they're capable of being "totally" smart.  The proxy in the middle
>>  will have to retain some intelligence and reference some type of
>>  permissions model or database to allow calls through or not.  I trust
>>  that industry (and quasi-industry, like Asterisk) programmers will
>>  come up with dozens of ways of intercepting and thrashing unsolicited
>>  phone call, so long as there is no back door that the spammer can
>>  sleaze through to get right to the desktop.
>
>It challenges the concept of e164.arpa.

I do not agree with that at all.  You're putting words into the 
mouths of the users of the service.  Not everyone wants their phone 
on the open Internet; most people don't, actually (regardless of 
opinions on this list.)  If the "do not call" database of standard 
telephony in the USA is any reflection of typical opinion on how 
telephony should be regulated from unrestricted inbound calling, I 
would say that most people will be overjoyed to have their calls 
filtered by an intelligent proxy in the future, so long as they have 
control of the process.  I suspect that my SIP device will not have 
much say in this future world of authentication, other than taking 
it's marching orders only from authenticated sources, and perhaps 
having some features to allow me to (during/post call DTMF, or 
screen-based, or voice commands, or whatever) add a caller to a 
whitelist or blacklist.

This says nothing about the option of keeping your phone unprotected 
and accepting any call.  e164.arpa doesn't make any judgement on what 
the endpoint is of a call, be it a proxy or a UA or something else, 
nor does it speak to the acceptance of a call - it merely says "if 
you want to reach this number, send the call to this IP address for 
further instructions."

>  > TLS SIP is also a nice concept, since it would require some sort of
>>  "root" authentication that could be revoked or at least recognized if
>>  a spam origin was adequately recognized.  This is all starting to
>>  sound a lot like an anti-spam thread, so I'll stop here.  Most
>>  intelligent people on the list should be able to figure out a bunch
>>  of ways to prevent spam, but the primary one is accountability of
>>  origin.  Anything that allows that accountability to be compromised
>  > from the perspective of the destination means that spam will
>>  inevitably slide in, so it is our job to enforce sane
>>  authentication/authorization mechanisms NOW on the vendors from whom
>>  we buy equipment/firmware.
>
>Right, the sole purpose of the original post (in asterisk-dev) was 
>to figure out how aware people are of this potential problem and 
>also if people think of this as a problem.
>
>/Soren

Surprisingly, Asterisk is light-years ahead of almost all the UAs and 
systems I've seen, and really has all the tools required to implement 
almost any type of method you want.  This becomes not an Asterisk 
question, but probably a distributed whitelist/blacklist question via 
an AGI or ENUM, which I don't think directly reflects on Asterisk as 
a development effort for Asterisk alone.  Granted, that database can 
be populated by Asterisk users, but I don't think much development is 
going to be required (if any) to do it - just a good lawyer, a robust 
and distributed network of core data systems, and someone who has the 
cycles and deep pockets to champion something for a monetary loss. 
So, Duane, want to put your ENUM tools to good use?  (see my post of 
a few minutes ago on "Blocking the do not call list" - it's 
marginally relevant.)

JT