A security researcher has built a system of detection of illegal images, which costs less than $300(£227) and uses less energy than a light bulb.
Christian Haschek, who lives in Austria, came up with the solution after having discovered a picture showing sexual abuse on children has been uploaded on its image, to its hosting platform Pictshare.
He called the police, who told him to print it out and bring it in.
However, it is illegal to possess images of child abuse, digital or on paper.
“Um… not what I planned to do,” Mr. Haschek said.
Instead he believed the solution to identify and remove explicit images.
Mr. Haschek used three Raspberry PIs, power of two Intel Movidius sticks, that can be trained to classify the images. He also used an open-source algorithm to identify explicitly called NSFW (Not Safe For Work), available for free from Yahoo.
He set it to find images which the system could say, with 30% or more certainty are likely to contain pornography, he said that he has adjusted the opportunity down to be sure not to miss anything.
Since then, he has discovered 16 more illegal images featuring children on his platform, all of which he has reported to Interpol and deleted.
He then contacted a larger image hosting service, which he declined to name, and found thousands of others running the downloaded images on their platform through its system.
“When I started working on my open source image hosting service PictShare I don’t think anyone but me would use it,” Mr. Haschek said on his blog.
“Over the years, the use has increased, and with the increase of the use of a website where you can upload images anonymously, there will be those who download illegal things.
“There are thousands of images on PictShare – I can’t look ahead, even in a year, so I had to think of something else.”
Professor Alan Woodward from the University of Surrey, said Mr. Haschek of the project has been encouraging.
“Law enforcement agencies around the world have struggled to find this horrible material and have it taken down. Unfortunately, the police have to work with high technology companies and that takes time,” he said.
“I like the idea that this particular site has taken its responsibilities and has found a solution to mitigate the problem.
“The scale of the challenges faced by large high-tech enterprises is certainly huge, and although these solutions could be scaled up, it takes money and effort. However, where there is a will there is a way.”