Declan McCullagh reports on a congressional hearing on porn on peer-to-peer networks:
Randy Saaf, president of P2P-tracking firm MediaDefender, said his investigations of child pornography on P2P networks found over 321,000 files “that appeared to be child pornography by their names and file types,” and said that “over 800 universities had files on their networks that appeared to be child pornography.”
Edward Felten comments on that:
It’s no excuse to say that it’s infeasible to sample 321,000 files by hand to see if they are really porn. Because if you actually care whether 321,000 is even close to correct, you can examine a small random sample of the files. If you sample, say, ten randomly chosen files and only five of them are really porn, then you can be pretty sure that 321,000 is far wrong.
His main point is certainly correct — examining filenames and types alone isn’t close to enough here. A distinction was lost somewhere, though, between “child pornography” and “pornography”. Assuming a halfway reasonable set of keywords were used to get the 321,000 figure, from my experience I’d guess that nearly all 321,000 files are pornographic. I’d be surprised if more than a handful of them are actual child pornography, though.
 Girls Porno Gay Vagina Adult Tit seXxx Cum Ass Anal Lesbian Nude Pussy Young Raped Fucking Fetish Mas.jpg)
As two for-instances, from a recent foray onto a p2p network, I present two graphical files. The one on the left is entitled “Alyson Hannigan, Charisma Carpenter, Sarah Michelle Gella Lolitas Lesbians Fuck Cum Blowjob Sexy Porno Xxx Gay Ass Anal Pussy Naked Young Girls Bondage Rape Preteen Tits Cunt Vagina Fetish.jpg”; the one on the right is “Sarah Michelle Gellar & Alyson Hannigan Nude (1) Girls Porno Gay Vagina Adult Tit seXxx Cum Ass Anal Lesbian Nude Pussy Young Raped Fucking Fetish Mas.jpg”. “Lolita”, “Preteen”, “Girls” and “Young” are all likely candidates for MediaDefender’s keyword list, and these files fall into most definitions of pornography, but they aren’t child porn by any means.
Another common ‘for-instance’ are advertisements for pornographic websites, which masquerade as other types of pornography, presumably to be downloaded by likely consumers.