On the one hand, that's so smart I can't believe it's not widely used by everyone.

On the other hand, if it was that common, there would be a market for systems that defeat it for the spammers.

If bypasses were common (mostly just sending "1"), then a configurable number you could cycle would work fine. Everyone would have a different number and you only get 3 tries.

Anything more complicated like actually following the voice prompt isn't going to happen soon.

voice recognition is already to the point where it can recognize numbers. That we are limited to one of 12 numbers (including * and #) before it gets too hard for humans limits the problem scope to the point where it is a relatively easy problem.

Of course this assumes enough people follow the pattern of press some number to continue. Every time the pattern changes the cost of understanding it and fitting it into their system goes up. In the end though it isn't a scheme we can win: AI can successfully follow more complex processes than humans can in this limited space - including random failure to follow the instructed process if it is too complex.

It can be done by asking some obvious question for humans:

"This is a anti-robocall system, please answer the question to complete the call. A mother cat and her three kittens are sleeping in a box. Dial the number of animals in that box."

The number of kittens change randomly and maybe the system can put some pillows, blankets and other non-animals in the box too, making automated processing harder. AI will get there, sure, but this will make things expensive for the attackers.

Your example is a trick question that will catch some real humans.

Some might consider that a feature.

I've always thought that binding robocallers in a contract that they must accept to speak or leave a message would be fun. Notify the caller that you charge a fee that's your state's maximum small claims award and add that the fee to be waived at your discretion for legit business. The big problem is spoofing and overseas calls, but I'd bet you could nab a few cases.

I'm thinking something like, "All unsolicited calls concerning the sale, lease, rental, or exchange of goods and/or services, regardless of past contact between calling parties or their third party affiliates, will incur a $5000/hr convenience fee, minimum billing for 1 hour, to be paid to _your name_ at POBox ... in full within 90 calendar days of the current date. This fee may be waived at _your name_'s discretion. Press 1 to accept or hang up to decline."

Bonus points if you fit the fee discussion in before the call center switchboard hand-off to a live operator.

I actually got so fed up with robocallers, and really people just calling me in general that I looked into setting up a 900 number. If people really want to intrude and take up my time, they can compensate me for it.

Unfortunately, 900 numbers apparently went away in the 2000s. Such a shame, it really would have solved the problem quite efficiently.

Wasn't there some kind of scam people used to pull where they'd add a prefix to a cell phone's outgoing calls, such that it bounced through a paid service relay? If I recall, someone would nab your phone, add the dialing prefix to the settings, and then return the phone to you. From that point on, all outgoing calls would actually be calling a 900 number, which then just called the outgoing number. The phone's owner would then get caught with a massive bill from the 900 number. It was an updated version of one of those original 'boxes', maybe a modified brown box? I forget all the phreaking terminology now, but I wonder if there's another olde timey phone phreaker trick that could be exploited.

I have run asterisk for 15 years now, everyone in the house has a 1 digit extension number (that way we can have private voicemail) I haven't had a robocall in years