[VoiceOps] STIR/SHAKEN warning!

[Paul Timmins]

Always worth pointing out that in March 2020, Somos rolled out TFNIdentity. We have it set up on customers who want to source from their TFNs, I haven't seen many carriers actually look it up, but it does exist.

> On Jul 7, 2023, at 5:34 PM, Nathan Anderson via VoiceOps <voiceops at voiceops.org> wrote:
> 
> I suspect things might be different now (& I just haven't kept up), but although it is clearly *possible* to transmit a TFN as the calling number / CID, I seem to remember that even just a mere few years ago, it was HIGHLY discouraged, and if you ever were to receive a call bearing a TFN as its CID, it had a very high likelihood of being fraudulent or spam.  This was of course back when the vast, vast majority of TFNs were essentially implemented as a call forward or alias to a number that hung off of a local exchange.  So of course outbound calls that many? most? companies with TFNs would make would typically be sourced from their local exchange number(s) and not from the TFN(s) (unless maybe a given company had a PRI and their provider allowed them to source calls from their TFN?).  Thus the expectation for a long time (as I understood it) was that TFNs were truly inbound-only and should be treated as such.
>  
> Loosely tangentially related, as a purely anecdotal report, I will note that I have yet to see a S/S signature/PASSporT attached to ANY calls made *to* ANY of our TFNs, via any of the 3 SIP wholesalers we have used as both RespOrgs & for actual traffic.
>  
> -- Nathan
>   <>
> From: VoiceOps [mailto:voiceops-bounces at voiceops.org] On Behalf Of David Frankel via VoiceOps
> Sent: Friday, July 7, 2023 7:52 AM
> To: 'Ivan Kovacevic'; 'Voice Ops'
> Subject: Re: [VoiceOps] STIR/SHAKEN warning!
>  
> Ivan asks: “How are you handling TFN atestations?”
>  
> When the signer of a call gives A-level attestation, it means that the signer knows that the caller “is authorized to use” the calling number.
>  
> The signer can “know” that in any of a variety of ways. For toll-free numbers, the most sophisticated and secure is probably via Delegate Certificates. SOMOS, the North American Toll-Free Number Administrator, has commented about this in a current FCC proceeding: https://www.fcc.gov/ecfs/document/10605623514445/1
>  
> As the signer, there are other ways you could determine that the caller is authorized to use the number. For example, you could solicit some documentation from them (like an invoice from their RespOrg and/or service provider) and you could call the number and verify that your caller answers. The regulations (today) do not specify exactly how you “know” so you (as the signer) need to act in the spirit of the rules.
>  
> This problem is not unique to toll-free numbers. I might have a geographic number that I obtain from provider A (and that’s how I get inbound calls to the number), but I make outbound calls from that number via providers B and C for redundancy and cost reasons.
>  
> Bear in mind that providers can set their own rules for what calls they will accept and what attestations they will assign, and those rules can be more restrictive than what might be dictated by regulation. For example, a provider might say “I will only assign A-level attestation to calls that use calling numbers assigned by me.” That’s their prerogative.  In fact, a provider might say: “I will only accept calls that use calling numbers assigned by me. Those calls will get A-level attestation. I will reject all other calls.” There are no rules (to my knowledge) that prohibit providers from setting these kinds of rules.
>  
> From: VoiceOps <voiceops-bounces at voiceops.org <mailto:voiceops-bounces at voiceops.org>> On Behalf Of Ivan Kovacevic via VoiceOps
> Sent: Friday, July 7, 2023 7:27 AM
> To: Voice Ops <voiceops at voiceops.org <mailto:voiceops at voiceops.org>>
> Subject: Re: [VoiceOps] STIR/SHAKEN warning!
>  
> Hopefully on-topic. How are you handling TFN atestations?  
>  
> Although a part of NANP - it's a different technology at the network level in terms of chain of authority and routing.
>  
> RespOrg manages the number, but can provision and use many carriers to make outbound calls using the TFN Caller ID (and to receive inbound calls via the same TFN)... RespOrgs is not necessarily a carrier - who and how checks that RespOrg has the authority in case of delegated attestation. I may be overcomplicating it in my mind.. but it doesn't feel like the regulation maps 1-to-1 over to TFNs... Just wondering what everyone's experience is. 
>  
> Thanks,
>  
> Ivan
>  
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