Why do gay apps struggle to stop catfish?

In a bid to tackle fake profiles and fraudsters, a popular gay dating app plans to offer a sort of "verified" badge to identify authentic members.

Hornet will be the first of the major gay social networks to let people earn a badge of authenticity.

The aim is to give users more confidence that they are talking to a genuine person.

But rather than moderators checking ID, the app will use algorithms to decide who gets a badge.

So can machine learning solve the problems that persist on dating apps?

Anyone who has used a gay dating app will be familiar with fakes.

Messages arrive from improbably handsome strangers, often angling for intimate photos or sexy chat.

These so-called catfish profiles use pictures stolen from popular social media stars or adult-film actors.

They lure people into conversation, sometimes trying to arrange dates they will never show up for. In more serious cases they try to defraud, blackmail or harm their victims.

So why do gay dating apps not offer a "verified" profile badge, like on Instagram or Twitter?

It is not that simple.

"Not everyone wants to or even should be identified," said Eric Silverberg, chief executive of dating app Scruff, which competes with Hornet on the app stores.

"People often create new, repeated or anonymous profiles, for many valid reasons," he told the BBC.

"Once you start verifying some, you create a kind of hierarchy on your platform that could lead to unintended consequences for people who are not out of the closet."

More than 70 countries around the world have laws against LGBT people.

ID checks would create a list of "verified LGBT people" that could be used by those wanting to do harm, including governments.

They would also raise barriers for those exploring their sexuality. If most users chose to verify their profiles, newcomers may find fewer people speak to them if they have not gone through the verification process.

Hornet says its system will not involve checking ID.

Instead, algorithms will evaluate how people behave on the app over time. Profiles that are judged to be genuine will display a "Hornet badge" as an indicator of trustworthiness.

The company said it would not disclose exactly how the algorithm works because that might help catfish work out how to trick the system.

But Hornet chief executive Christof Wittig told the BBC: "We look at people and how they earn trust while they interact with the community. It requires people to be authentic and interact."

Hornet combines the social elements of apps such as Instagram with the meet-up aspect of apps such as Grindr.

The "verification" system will analyse how people use those features, to weigh up whether the activity is consistent with genuine users.

Mr Wittig stressed that the algorithm would not look at the contents of private messages.

And because many people in countries with anti-LGBT laws do not use a selfie as their profile picture, the system will not involve any image analysis of profile photos either.

Of course, fake profiles can be very convincing - they are carefully crafted to be deceiving.

Could a catfish profile earn a "Hornet badge" and add a mark of authenticity to their fake profile?

"In theory, yes," said Mr Wittig. "There will always be that one person who will put this super extra effort in, and there will always be some that fall for it.

"But with this system, the amount of work versus the probability of reward changes. We are making being a fake profile very costly. They can no longer do it at scale.

"And even then once you know somebody is a catfish, their pattern is better understood. The machine learning has much more data to really understand how catfish behave."

What about members who do not want a "Hornet badge" because they are worried about being exposed for using an LGBT app?

Mr Wittig said it would not be possible to opt out of the system but he said members would still be able to be discreet about their identity.

"People in some countries don't put a face picture up because it's so dangerous, but they can still be verified by the system," Mr Wittig told the BBC.

The BBC invited rival dating apps Grindr and Scruff to share their views on user verification methods.

Scruff told the BBC: "The bigger question is why bad actors continue to proliferate on some platforms, and the answer always comes down to one thing - leadership."

"We have always prioritised moderation and community support, because we are building an app that we ourselves use and share with our friends and loved ones. When people misuse our platform, we react swiftly and decisively.

"We have spent years building advanced technologies to stop spammers, catfishers, and other bad actors."

Grindr has yet to respond.