There is also the free exchange or trade of pornography between individuals, often through email . The federal government has long been involved in sting operations where they attempt to get people to send them child pornography through email attachment, and most ISP's are happy to cooperate with those investigations. There is some child pornography available through webpages. The more typical material seems to be depictions of child nudity, depictions of children in erotic poses, and depictions of sexual activity between same-sex children. The question of why child pornography is centered on the nudity and sexual arousal of a single child, or of same-sex children, may tell us something about pedophilia.
Pedophiles tend to fantasize about loving, equal, consensual sexual relationships with children.
Depictions of adult-child activity may interfere with these fantasies. Additionally, depictions of secondary sexual characteristics may be a turn-off, even if one sexual actor is a child. It may also indicate that the pedophile has not come to terms with his own adult sexuality. The person who has a collection of child pornography that centers on explicit acts of penetration of children by adults, is probably more dangerous than the person whose collection centers on children. Much child pornography on the internet was produced in the 1950's through 1970's.