Editorial: Big companies need to use PhotoDNA

As disturbing as the current explosion in child pornography on the Internet is this thought — all those creeps were out there all along.

The Internet simply made it easy for them to find each other.

Fortunately, as reporter Dan Rozek pointed out in Sunday’s Sun-Times, the Internet also makes it far easier for the police to hunt down the producers and consumers of child pornography, and in ways that do not inevitably infringe on the privacy rights of other Internet users.

One particularly effective technology is PhotoDNA, developed and offered for free since 2009 by Microsoft. Illinois Attorney General Lisa Madigan is urging all big Internet companies, beginning with the likes of Google, to adopt it, and we echo that call. It’s a matter of fighting fire with fire.

PhotoDNA allows investigators to track online child-porn files from user to user, anywhere in the world, even if the images are altered in some manner, such as by cropping. PhotoDNA works by creating a digital code for an image — a series of numbers called a “hash value” — and then searching for this image within large data sets, much in the same way antivirus software seeks out malicious Internet bugs.

The aim is not only to catch child pornographers and pedophiles but to send them the message that online services are hostile — don’t even try it here. Facebook, the largest photo-sharing site on the Internet, began using PhotoDNA this spring.

At the moment, PhotoDNA can search for about 10,000 images collected by the National Center for Missing & Exploited Children, which has a Congressional mandate to act as a clearinghouse for such material. PhotoDNA is designed to cull through huge amounts of data quickly and accurately enough to, in the words of the New York Times, “police the world’s largest online services.”

By the late 1980s, non-digital child pornography — of the sort found on paper, film and videotape and covertly sent through the mails — had been virtually eradicated. But with the advent of home computers, the Internet and online credit card transactions, child porn has become more widespread than ever. In 1995, the National Center reports, federal authorities prosecuted only about 50 people for child pornography nationwide. Now, they’re prosecuting about 2,500 a year.

The National Center estimates that since 1997, the number of child pornography images available on the Internet had increased by 1,500 percent.

When we hear of law enforcement efforts to search electronic files in any manner, our initial response is always skepticism. Far too many unconstitutional infringements on our civil liberties, such as tapping our overseas phone calls and rifling through our library records, have been rationalized by both the Bush and Obama administrations in the name of “homeland security.”

But PhotoDNA is not a technology naturally suited to unwarranted wholesale snooping. It is triggered only by actual evidence of a crime — child pornography — and, if kept to that, would seem to pose no major civil liberties concerns.

Illinois, under Attorney General Madigan, has come to be seen as a leader among the states in the fight against Internet child pornography.

Let’s keep it that way.