Re: Something doesn't add up...
> Our voice processors ... could set any originating telephone number, or none.
But your telco would block any numbers that weren't permitted. In simple cases, that would be numbers on that line, but I'm sure there were processes to allow other numbers (such as the main call centre contact number for large orgs) to be used.
The problem is that with the rise of really cheap international calling (via oversees carriers with little motive to do the right thing), and VoIP, there are links in the chain that are much much weaker. I deal with VoIP at work, and the provider we use basically relies on the reseller to vet applications for "foreign" CLI presentation. As we are a reseller, I could easiler permit myself to spoof any number and in reality there's not a lot anyone can do about that.
I think the main target should be within the industry, and telcos where the CLI isn't trustworthy should get some sort of restrictions placed on them until they either go bust or improve their processes. So basically, if a telco is caught allowing spoofed CLI - they should have all their CLI blocks and all their calls flagged as number not available or number withheld (that would allow easy call screening) and unless the telco's only customers are spammers, they'll be under commercial pressure from their custoemrs to "fix the problem". Or even just refuse to accept calls from such carriers.
Now, if the ICO named and shamed the carriers responsible, there's scope for an industry blacklist and a new product to sell to customers "call blocking from spam friendly carriers". Don't expect it from any of the big names, they won't want to miss out on the revenue they get for terminating the calls.