Hundreds of thousands of people fall victim to scams in the UK every year.
Many are run from criminal call centres abroad, where teams of fraudsters operate around the clock.
One man in the UK, who goes by the name “Jim Browning”, decided to do something about it. He hacked into a call centre in India from where scammers target their victims.
Jim gained access to the recorded scam phone calls as well as CCTV footage exposing the scammers at work.
What Jim did was illegal – but he says he wants to stop the fraudsters, and he passed his footage on to BBC Panorama.
Journalist / Producer: Sam Judah
Reporter: Rajini Vaidyanathan
If you are in the UK, you can watch Panorama: Spying on the Scammers on Monday 2 March at 20:30 on BBC One or catchup afterwards on iPlayer.