'I put a troll in jail using my PlayStation'
In myth, trolls lurk in the dark under bridges, waiting to pounce on innocent passing travellers.
Modern day trolls hide behind avatars and fake profiles to launch vicious and terrifying verbal attacks on the users of social media.
Journalist Mike Deri Smith wondered how easy it would be to unmask them.
He's tracked down trolls around the world - starting with 25-year-old John Nimmo from South Shields, who'd targeted feminist campaigners.
"After the case of Caroline Criado-Perez, the campaigner who fought to get a woman onto a £20 note, it seems quite a lot of internet users, generally men, had a problem.
"The hatred was so easy to find. You'd just look on Twitter and you saw some really vicious stuff. About raping her. Finding out where she lives. Killing her.
"I thought I'd engage some of these people in conversation, work out why they thought this was an OK thing to do.
"One of the worst offenders seemed very eager to talk through Twitter. He was very proud, very happy to explain his reasons, even though I said at the start, 'I'm a journalist.'
"He thought the police would never come to him. He said he wasn't scared of the police, he'd never get caught. That was later read out in court.
"I gradually tried to create a good relationship with him, even though he was a detestable, horrible person.
"I tried to be nice and very engaged with what he'd been saying. I was saying 'LOL' to all the stuff he was writing.
"I wanted to be in conversation with him for hours - to gain his confidence - so that eventually he would give me maybe his name, his location or just anything that would give me a hint of who he was.
"I wanted to know what sort of people would post this sort of abuse on the internet.
"Eventually it got down to me saying, 'Oh, I'm going to go and play PlayStation.'
"I thought, 'It's a young guy, he probably plays a lot of Call of Duty.' Immediately he said, 'Please add me on PlayStation. We can play.'
"It was that one slip-up - where he gave me his username on PlayStation, which he'd also stupidly listed on his Facebook page - that meant I could work out who he was.
'Seeing him, made me realise how empty his threats were'
"Looking through his profile, I don't know if there could have been anyone who was more stereotypically a troll.
"He seemed to be quite young, he seemed to really like video games, he didn't seem to have a job. I was amazed.
"He was the sort of person no-one would be afraid of.
"He really terrified the women he was writing to, it was savage stuff... which he eventually went to jail for, but seeing him made me realise how empty his threats were.
"We tracked down where he lived. We spoke to his father, who gave us his phone number.
"He initially denied all of it, but you could hear in his voice that he never thought what he was doing online would bleed into the real world, that all this horrendous abuse would come back to him.
"The police arrested him two days later. He was jailed for eight weeks.
"Since finding out who he was, I've tracked down and unmasked a number of trolls - whether they're sending abuse online, or promoting Islamic State.
"I never feel any sense of pride in working out who these people are.
"I just had the sense that they should actually take responsibility for their actions. It's a similar story with all of them.
"They are all very boastful and very arrogant online, but the moment you confront them they very quickly beg you not to reveal who they are. They say they didn't mean any of it and they're really, really scared.
'Do I want to lose my job?'
"When you do unmask them, you realise what sad cases they are. They just want to get a rise out of their victims. They aren't even playground bullies. They're not strong, they don't have any way of physically harming you.
"They all know the stuff they're saying is awful. Really bad. They crumble. They realise they're not the people they pretended to be online. They're weak people who don't stand by what they've said. You get the sense they had no idea what's right and wrong online.
"Trolls need to realise that if even I can find you, the police will very easily find out how you are. Unless you're some mastermind, it's so straightforward.
"And the police are taking this increasingly seriously. Trolls need to think, 'Do I want to lose my job? Do I want to be outed over this stupid abuse online?'"
If you or your friends are experiencing any negativity online, search for BBC Advice where you can get loads of info and support.
Mike Deri Smith is currently a producer working for Channel 4 News