Every year tens of thousands of people are conned by online scammers, but it is not only the authorities taking action: a network of tech-savvy volunteers is also working to expose them.

"We waste scammers' time, we waste their resources and we make them believe they are not as good as they think they are," Jill - not her real name - explains to the BBC's Victoria Derbyshire programme.

She is part of a global network of so-called scam baiters, who spend their evenings trying to unearth online con artists by pretending to fall for their tricks.

The ruses can range from emails saying the recipients have won the lottery, to "long-lost relatives" who have left them an inheritance.

"Scammers are always going to be there but if we can take them down a peg and take a victim away from them any time we can, then we are doing something good," Jill adds.

One of the main techniques, explains Wayne - a scam baiter who often works with Jill - is by leaking scammers' details and their conversation scripts online.

The aim is for these to filter through to search-engine results, so potential victims will be alerted if they type in the scammer's name.

Wayne says police and other authorities use the data, too.

The scam baiters say they do not earn a penny from their work and that they have other reasons for taking on the con artists.

One man from the US, who wished to remain anonymous, wanted to turn the tables after his mother was caught up in a "grandparent scam", and came close to losing $5,000 (£3,900).

For Wayne, the motivation is simply the "buzz" he receives from knowing he can help someone.

He says people have contacted him via his website on the verge of suicide.

Questions remain, however, over whether scam baiters are sufficiently equipped - or best placed - to deal with scammers rather than the authorities.

Official advice is to report any suspected offenders to Action Fraud - the UK's national fraud and cyber-crime centre, which focuses much of its resources on prevention and raising awareness.

And Wayne says scam baiters do point people towards the official routes when they feel out of their depth.

But Jill argues they still play an important role, as advances in technology and the fact many of the scammers are overseas mean it is difficult for authorities to catch such criminals.

And they reject the label vigilante. "Vigilantes work outside the law," says Wayne.

'Twisted' humour

Wayne's set-up is rudimentary. He works under various aliases, mostly named after characters from his favourite children's television shows of his youth.

He often makes himself seem more vulnerable - and potentially gullible - by pretending to have recently broken up from a partner.

"To bait you do need to have something of a twisted sense of humour," he jokes.

Both Wayne and Jill always wait to be approached by scammers, rather than seeking them out.

But they don't have to wait long. Their names are on a so-called "suckers list" - effectively a database of people thought to be easy to con - which is passed around by scammers online.

The latest to get in touch is a man who emails Jill to say she has won the lottery in Africa.

Pretending to be husband and wife, Wayne and Jill make a joint call back, the aim being to waste the scammer's time by arguing about which one of them gets the money.

Death threat

They often have other scam baiters on stand-by who can be brought in to play other characters in their facade, to confuse the scammer - and waste their time - for as long as they wish.

Surprisingly, Jill considers her biggest success to be the time she received a death threat from a scammer she had targeted.

"If you get a death threat you know you've really wound someone up. I had one scammer driving round Madrid for a day trying to find 'Lynn', who had gone to Madrid.

"Of course, I hadn't gone to Madrid, I was in my front room. He got so upset and said, 'I'm going to come and find you. I don't care what the penalty for murder is in the UK, I'm going to find you'."

Jill tells it as a funny anecdote, but it underlines the dangers involved.

"I take great care in protecting my online persona," she says.

"I bait with email addresses that aren't traceable. I don't use any of my real-life information. All of my characters are based somewhere 100 miles away from where I live."

Asked whether the death threat suggested scam baiters were taking their cause too far, she firmly disagrees.

"None of us are taking this far enough. These people are criminals. They don't deserve our sympathy.

"They rob our elderly relatives, so they deserve to be treated as criminals. If we could get them arrested, we would."