Even the experts were puzzled by the ciphers in some of these searches. About 53 percent of search terms and 88 percent of the search results contained code words that had not been tallied by CEOP. The agency may have eventually discovered them during the course of their investigations, but Rashid's team realized they could stay ahead of this "cat-and-mouse game" with the help of a computerized strategy.
As a proof-of-concept, human volunteers unversed in the child-pornography lexicon were given 10 popular Gnutella code words, such as "ITA" (Italy) or "PTHC" (Preteen Hardcore) and then asked to guess which were related to child pornography. The volunteers succeeded less than half of the time. But after these same volunteers had a chance to look at the entire search query in which these key words were nested, their success rocketed to 94%.
Rashid now needs to use this principle, termed collocation, in a module that will provide law enforcement with an evolving "dictionary" of the code words. The second phase of Isis, for monitoring chat rooms, is still in its infancy but will require analyzing not just code words but word frequency and sentence patterning.
Other technological efforts have focused on developing image analysis software for the National Child Victim Identification Program database and in developing surveillance systems. For example, the FBI's now-retired Carnivore, which did not use linguistic analysis, but could "sniff" email traffic and monitor keywords.
Some experts have reservations about the Isis plan, particularly if it allows law-enforcement agencies to amass dossiers on specific individuals outside of a criminal investigation. "If this is something that any government is mandating a social-networking service do," says John Morris, general counsel for the Center for Democracy and Technology, "then that raises enormous challenges." He says he would have no problem with social networks voluntarily cooperating with law-enforcement agencies and disclosing their privacy practices to customers—as they do now—but a government mandate would place an enormous burden on sites that play no role in the distribution of child pornography and threaten the privacy of law-abiding citizens. "A huge problem with any sort of mandate is it is very hard to define what a social-network site is without sweeping in every blog in this country and Ebay and Amazon, all of which allow you to have profiles about yourself."
Anthony Finkelstein, a computer scientist at University College London who has worked on privacy tools to help agencies share data about child welfare cases, simply feels like the Isis Project's blanket monitoring strategy is misguided. "Do I regard this as being a critical issue? On balance, I'm not 100% convinced, but I think it's worth some further investigation." His biggest concern is that Isis, like a neighbor's infuriating home alarm, is bound to produce a lot of false positives that need to be investigated by law-enforcement officials. "Even if you are able to identify those false positives," he says, "it takes effort to do so, and that's effort that's not devoted to something else."
Finkelstein believes investigators should stick to traditional intelligence-gathering efforts rather than a blanket monitoring scheme and that improved funding of social programs for teenagers could prevent them from falling victim to online pedophiles. Indeed, one recent study of online crimes against children estimates that deception took place in only 5 percent of these cases, and most illicit activity involved teenagers who were aware they were meeting an adult who was looking for sex.