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There are significant downsides to technically prohibiting caller ID spoofing. First, you would no longer be able to preserve caller ID when forwarding calls.

by agwa 12y ago

There are significant downsides to technically prohibiting caller ID spoofing. First, you would no longer be able to preserve caller ID when forwarding calls. Consider how much less useful Google Voice would have been if you couldn't see the caller ID of calls forwarded to you. Second, in VoIP, outgoing calls (termination) and incoming calls (origination) are completely decoupled services. This is really nice because it enhances reliability (you can fail over to different termination provider) and reduces costs (you can route outgoing calls to the cheapest provider depending on the destination). A BCP38-style system would require you to purchase your termination from the same provider as your origination in order to have outgoing caller ID.

6502nerdface 12y ago
I think the idea is that caller ID forwarding should be implemented in some authenticated or verifiable way. I hesitate to call credential forwarding a solved problem, but surely a modern protocol design could do a lot better than the current free-for-all, I-am-who-I-say-I-am system.
- cmdrfred 12y ago
  Maybe something like DMARC but for phone numbers, you should be able to set your phone number to be rejected if it is spoofed.
wtallis 12y ago
As a Google Voice user, the downside would be sad but totally worth it if it meant I could have GV accurately screen my calls. I could still get full caller ID information for GV calls received through VoIP, and when receiving calls through POTS I could at least know that the call is from somebody I'm willing to take calls from. The other use case applies pretty much only to people I don't want to hear from in the first place, so I have no sympathy for how it would hurt their bottom line.
- agwa 12y ago
  It sounds like the list of people you're willing to receive calls from is pretty small. Have you ever actually received a phone call which spoofed the caller ID of someone you know? I haven't - all the spoofed calls I receive are from numbers I usually wouldn't answer anyways since I don't recognize them. Also, note that Google Voice no doubt uses many termination providers (considering they're giving the service away for free, they'll need some pretty sophisticated routing to take advantage of cheap rates), so the second use case applies to any Google Voice user.
  - wtallis 12y ago
    Why can't we have a system whereby Google is required to prove to each of their termination providers that they legitimately own and control my GV number, and thus all of those providers can assure my outgoing GV calls have valid caller ID data? I don't see where it should matter whether calls into my number take a potentially different route from calls from my number.

by agwa 12y ago

6502nerdface 12y ago

I think the idea is that caller ID forwarding should be implemented in some authenticated or verifiable way. I hesitate to call credential forwarding a solved problem, but surely a modern protocol design could do a lot better than the current free-for-all, I-am-who-I-say-I-am system.

cmdrfred 12y ago
Maybe something like DMARC but for phone numbers, you should be able to set your phone number to be rejected if it is spoofed.

wtallis 12y ago

As a Google Voice user, the downside would be sad but totally worth it if it meant I could have GV accurately screen my calls. I could still get full caller ID information for GV calls received through VoIP, and when receiving calls through POTS I could at least know that the call is from somebody I'm willing to take calls from. The other use case applies pretty much only to people I don't want to hear from in the first place, so I have no sympathy for how it would hurt their bottom line.

agwa 12y ago
It sounds like the list of people you're willing to receive calls from is pretty small. Have you ever actually received a phone call which spoofed the caller ID of someone you know? I haven't - all the spoofed calls I receive are from numbers I usually wouldn't answer anyways since I don't recognize them. Also, note that Google Voice no doubt uses many termination providers (considering they're giving the service away for free, they'll need some pretty sophisticated routing to take advantage of cheap rates), so the second use case applies to any Google Voice user.
- wtallis 12y ago
  Why can't we have a system whereby Google is required to prove to each of their termination providers that they legitimately own and control my GV number, and thus all of those providers can assure my outgoing GV calls have valid caller ID data? I don't see where it should matter whether calls into my number take a potentially different route from calls from my number.