Jyothi Krishna is one of the most famous names to emerge from the film industry centred in the southern Indian state of Kerala. It's a smaller and more conservative filmmaking hub than the much more famous Bollywood, and mostly makes films in the Malayalam language, but it does produce about 200 films a year.

South Indian film stars rarely wear racy costumes or appear in photo shoots, yet some fans graft the heads of female actors onto naked or pornographic images which are widely shared on Whatsapp.

Krishna has hit back at this practice in a Facebook post. Writing in local language Malayalam, Krishna - who has 1.5 million followers on Facebook - said she was speaking up to "give other social media harassment victims like myself, the strength to express their voice and bring culprits in front of the law."

In an interview with BBC Trending, Krishna said she was first alerted to the image when "a good friend, who is also a top movie director, first notified me of its existence. Then several of my friends and relatives started messaging me to say it was being shared widely on social media."

Hers is far from an isolated case. Although not exclusive to Kerala, Krishna said that the sharing of Photoshopped porn in the region was a "huge problem" and that she has lodged a complaint with the police.

Last year, two teenagers from Kerala were charged under cybercrime laws for uploading a fake video of another Malayalam actress, Asha Sarath, on Whatsapp and Facebook. And a 19 year-old man was arrested for sharing "obscene and forged material in electronic form" of Kerala TV actress Gayathri Arun.

A local psychiatrist who has looked into the trend, Dr C P Somanath, says that Kerala has a high literacy rate and widespread use of mobile phones and computers, meaning many young men have access to the internet and the skills to manipulate photos.

"There is also a very conservative mind-set here," Somanath told Trending. "Actresses from this state wouldn't do the kind of roles or photo shoots where they expose their bodies, in the same way that their Bollywood or Hollywood counterparts would. It's possible that this suppressed sexuality and curiosity amongst a particular age group of young men in the state, coupled with the know-how of modern technology, may have found an outlet in the creation and sharing of these images."

According to a police study from 2012, a quarter of all porn uploaded in India came from Kerala. In the same year, the National Crime Records Bureau of India said that the state also had the highest number of under-18 teens arrested for violating the country's information Technology law.