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So-called spy-cam porn has existed in China for at least a decade, despite the fact that producing and distributing porn is illegal in the country. […] Last April, new government regulations attempted to stem this epidemic - requiring hotel owners to check regularly for hidden cameras.

[…] BBC World Service has found thousands of recent spy-cam videos filmed in hotel rooms and sold as porn, on multiple sites. Much of the material is advertised on the messaging and social media app Telegram. Over 18 months, I discovered six different websites and apps promoted on Telegram. Between them these claimed to operate more than 180 hotel-room spy-cams which were not just capturing, but livestreaming, hotel guests' activities.

I monitored one of these websites regularly for seven months and found content captured by 54 different cameras, with about half operational at any one time.

That means thousands of guests could have been filmed over that period[…]

[…] there are significant sums of money to be made. Based on channel membership and subscription fees, the BBC estimates AKA [a spy-cam porn trader] alone has earned at least 163,200 Yuan ($22,000, £16,300) since last April.

[…] There are strict rules on selling and using spy-cams in China, but we found it relatively easy to buy one in the country's largest electronics market in Huaqiangbei.

Accurate figures on how many people have been brought before the courts for spy-cam porn are more difficult to find. China's authorities have shared far fewer legal case details in recent years, but the cases we found ranged the length of China - from Jilin province in the north, to Guangdong in the far south.

Blue Li, from a Hong Kong-based NGO called RainLily - which helps victims remove explicit secretly-filmed footage from the internet - says demand is rising for her group's services, but the task is proving more difficult.

Telegram never responds to RainLily's requests for removal, she says […]

"We believe tech companies share the huge responsibility in addressing these problems. Because these companies are not neutral platforms; their policies shape how the content would be spread," Li says. […]

Contacted again 10 days later, with the BBC's full investigation findings, Telegram told us: "Sharing non-consensual pornography is explicitly forbidden by Telegram's terms of service" and "it proactively moderates… and accepts reports [of inappropriate content] in order to remove millions of pieces of harmful content each day."

We formally set out our findings to Brother Chun and AKA that they were profiting from exploiting unsuspecting hotel guests. They did not reply, but hours later the Telegram accounts they used to advertise the content appeared to have been deleted. However the website that AKA sold me access to is still livestreaming hotel guests.[…]