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GCN : September 2014
[BrieFing] Digital devices have provided law en- forcement agencies investigating child abuse and exploitation with an embar- rassment of riches. The devices can hold thousands of images that can be used as evidence and as clues to help identify and nd missing children. But the sheer volume of data being reviewed can slow an investigation to a crawl. Adding to the frustration, many of the images investigated already are known to investigators; they provide little new information and delay discovery of new evidence. "Everybody is looking at the same things over and over again," said Rich Brown, law enforcement liaison and tech- nology advancement of cer at the Inter- national Center for Missing and Exploited Children (ICMEC). "We felt we could really make a difference in the amount of time it takes an agency to go through mil- lions of pieces of child pornography." ICMEC developed Project Vic to promote cooperation and sharing among agencies through development of open standards technology. It hosts a database of digital hashes for several million images of child porn, using a variety of hashing algorithms. By help- ing investigators quickly identify known images, it lets them focus resources on unknown images that can lead them to new victims. This is part of a move away from "seize and prosecute" tactics focusing primarily on prosecution for possession of child pornography and toward a focus on helping exploited children. "What we're trying to do is go to a more victim-centric approach," Brown said. By aggregating data and using tech- nology to evaluate it, Project Vic aims to avoid duplication of effort and stretch tight law enforcement resources. The Project Vic image hash set is a good investigative reference, but hash- ing and comparing images is still time consuming. So Basis Technology, which maintains the Autopsy open source digi- tal forensics platform, developed a new advanced image analysis and categoriza- tion module to more quickly analyze and prioritize large sets of images. It uses algorithms to create a hash, or message digest, of les being examined, which can then be compared with the Project Vic collection to nd matches. "There certainly are more powerful tools out there," said Brian Carrier, VP of digital forensics at Basis. But the Autopsy analyzer's ability to abstract data and prioritize images quickly can help inves- tigators cut through the 85 percent of old material in a cache and focus on the 15 percent of new evidence. The Autopsy platform supports a variety of open source modules for digital forensics investigations. The image analysis module was developed last year under a contract with the Homeland Security Department's Science and Tech- nology Division to create tools for law enforcement. Agencies want open source tools because they are easy to use and cheap, Carrier said. The goal of the DHS program was to develop new capabilities rather than merely develop free versions of existing products. "We reached out to a lot of law en- forcement people to nd out what their greatest pain points were," Carrier said. "One of their common requirements was for dealing with the large amounts of images." Basis spent about ve months devel- oping the new Autopsy interface, which was released for beta testing this sum- mer. An early version of it was released at the Crimes Against Children Conference in Dallas on Aug. 11, and the nished version will be included in a new release of Autopsy. The strength of Autopsy's image analysis is its ability to return signi cant results early, while the analysis is going on, rather than dump all of the results together at the end of the process. The analyzer prioritizes material to be examined on a device, looking rst at user content before other les. It also looks at metadata, using Exif (Exchange- able image le format) standard data that is applied to images by digital cameras, scanners and other image-handling technology. The Autopsy analyzer interface is just one tool in the Project Vic toolkit that can be used to assess evidence and further an investigation. "It reduces the workload of the inves- tigators and lets them focus on new and unknown images," Brown said. • BY WILLIAM JACKSON Image analysis tools speed exploited children casework 4 GCN SEPTEMBER 2014 • GCN.COM "We felt we could really make a difference in the amount of time it takes an agency to go through millions of pieces of child pornography." -- RICH BROWN, INTERNATIONAL CENTER FOR MISSING AND EXPLOITED CHILDREN