and these days their appetite fed by free sites, with porn hub, youporn, red tube. known as tube sites. >> what is a tube site? >> think of youtube with naked people. >> reporter: like youtube, users can upload and share videos instead of cat and music, it is hard core pornography, much of it pirated. thanks to tube sites, porn has never been more accessible to anyone with a computer. an that should worry parents. is one of the effects of awful this free online porn the fact that anybody could get it in clueding children? >> there is no barrier of entry. no age verification. you:00 click on. get on. larger and larger every year. more and more content is free online. >> even as the popularity of porn increases, the industry is collapsing. >> you have to bring matching bra and panties. >> to see how things have changed. we muet up with two performers before their shoot for a studio called girlfriend films. >> anything you put on right now will be housewivy that's the character you are playing. >> reporter: at first they seem cheerful. >> i don't think you are the hous