MELISSA BLOCK, HOST:
We're going to hear next about a case that involves the former head of cyber security for the Department of Health and Human Services. He's being sentenced today in Nebraska for accessing child pornography. The case highlights a problem for prosecutors. They say tools that cloak online identities complicate their efforts to police all types of crimes. The Justice Department says the man used free software to try to remain anonymous. NPR's Carrie Johnson has more, starting with the headlines the investigation sparked.
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UNIDENTIFIED REPORTER #1: A federal cyber security director turns out to be a predator.
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UNIDENTIFIED REPORTER #2: Caught and convicted here in Omaha in one of the most horrific cases of child pornography we have ever covered.
CARRIE JOHNSON, BYLINE: Prosecutors say they found graphic images of children on a laptop computer in the home of Timothy Defoggi. He once led cyber security efforts for the Health and Human Services Department. But in this case, the Justice Department says Defoggi used his expertise to hide from the law, along with other users of child porn sites on a network called Tor. Tor provides popular software that helps people hide their location and viewing habits by bouncing messages all over the world. Supporters say it can be used for perfectly legitimate reasons, to protect the privacy of protesters and artists and repressive regimes. But it's also drawn attention from people like Leslie Caldwell. She runs in the criminal division at the Justice Department.
LESLIE CALDWELL: A lot of what we thought of as traditional unsophisticated criminals are now on the Internet selling drugs, selling guns, selling murder-for-hire schemes, selling child pornography.
JOHNSON: And those criminals, Caldwell says, have gotten a lot smarter about covering their tracks.
CALDWELL: Technology is trending toward even greater anonymization, which is something that is just going to make our job that much more difficult.
JOHNSON: In the Defoggi case, prosecutors say he took substantial steps to avoid detection. They say he used software programs to erase his web searches and had to be physically removed from his laptop when the FBI searched his home. Defoggi's lawyer at the time of the trial, John Berry, didn't return phone calls. But he talked with Omaha's KETV about the case last year.
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JOHN BERRY: Just because you have a screen name and IP address, that does not tell you who is behind the computer, especially when there are multiple people that live in a residence.
JOHNSON: And that's the anonymity problem in a nutshell. Except for this - prosecutors in this case were able to unmask many users of those graphic sites. The FBI seized the sites and watched for weeks, tapping communications and using other investigative techniques. Assistant Attorney General Leslie Caldwell didn't want to share details for fear criminals would work around them, but she says the government gets judicial approval to take those steps.
CALDWELL: Certainly in the criminal context, there are a lot of checks and balances and we work with the courts and under the supervision of the courts.
JOHNSON: Skeptics of government surveillance wonder if prosecutors tell judges exactly what they're doing and whether courts understand those steps. Julian Sanchez is a senior fellow at the Cato Institute.
JULIAN SANCHEZ: There is a problem of the gap in knowledge between the people implementing and deploying high-tech search methods and the judges that are supposed to be authorizing them.
JOHNSON: Sanchez says there are important trade-offs to balance between crime-fighting and privacy, and unknowns such as whether the U.S. has cracked the Tor network.
SANCHEZ: That's something that's important for the world to know. It's important for democracy activists and repressive regimes to know because if we can do it, probably China's intelligence agency can do it, too.
JOHNSON: Last week a computer science researcher at a conference in Germany reported 4 out of 5 visits to Tor hidden sites relate to child abuse or pedophilia. But no one knows how many of those visits come from law enforcement patrolling the web for criminals.
Carrie Johnson, NPR News, Washington.