Using disposable phone numbers for better security

Last night I received a call from my bank. They'd detected an unusual transaction and wanted to make sure that it was legitimate. Had I recently purchased £10,000 worth of crypto in the Maldives? What?!!? No! ARGH!

I started to panic. All my apes money gone!

No. Wait. The other thing. I knew it was a scam from the moment "James from your bank's fraud team" started his patter.

You see, I have multiple phone numbers. And "James" called me on a number which isn't tied to my bank. So I strung him along for half an hour or so pretending to move my money into a safe account, taking ages to wait for an SMS confirmation code, accidentally reading out the wrong one, before cursing him and his lineage even unto the seventh generation. He, in return, introduced me to a whole new range of swearwords from his native tongue and hung up on me. Charming!

Here's how it works, and how you can use this trick.

The easiest way is to get a dual SIM phone. I have my main SIM which holds my primary phone number. That's the number used by my family, my banks, and anyone vaguely trustworthy. My second SIM contains a free disposable PAYG SIM.

That phone number gets given out to retailers, couriers, Gumtree & Freecycle users, pizza delivery, and anyone else who doesn't need my number permanently.

My Android phone tells me which line is being called. And once I start getting too much spam to that number I throw the SIM away and get a new one with a new number.

If you have an eSIM, you can do the same thing. Find a cheap eSIM provider, sign up to a PAYG or monthly plan, then ditch the number whenever you like.

Or, you can set up a SIP calling plan. Install an app and have calls automatically routed to you.

About a dozen years ago, I worked with a UK mobile network to develop "disposable" phone numbers. The idea was that we would partner with, say, a dating app and generate a new phone number for you. Your date could call and text you without you having to reveal your real number. If they turned out to be a jerk, you could revoke the phone number immediately.

The same tech could work for hiring a plumber, getting a takeaway, or a hundred different use cases. The plan was to have an app which displayed a push-notification telling you which number was being called - so you knew if it was from your temporary lover or the person picking up your old sofa.

Sadly, the demo never went anywhere. It's a pity. I'd love to have a SIM with multiple disposable numbers.

But, for now, give out your temporary number to people who don't need a way to permanently contact you. Better safe than sorry!