CLEARWATER, FLA. - When it comes to cybercrime, one of the biggest problems facing the Department of Defense comes from within - the rank and file personnel suspected of downloading child pornography on military PCs.

Although fraud, network intrusions and counterintelligence cases also keep the department's tech experts busy, it's detecting evidence of child pornography stored or accessed via military networks that's straining the resources of the Defense Cyber Crime Center. At last week's Defense Department Cyber Crime Conference, which was attended by about 550 computer crime specialists from the military and FBI, the experts didn't shy from acknowledging child pornography as a scourge the military is determined to fight.

"Child porn is 50% of our criminal cases," said Steven Shirley, director of the Defense Cyber Crime Center. The computer forensics lab in Baltimore is regularly contacted by investigators in the Army, Navy, Air Force and Marines to analyze digital evidence seized as part of the military's most complex computer crime investigations.

Of the 411 cases referred last year to the Defense Cyber Crime Center, 39% were categorized as "criminal" and half of those involved child pornography, Shirley told conference attendees during a presentation.

He noted the terabytes of seized images and other data that accompanies child pornography cases can take analysts two to three months to plow through.

"There's often a backlog," said Bill Harback, senior computer forensic examiner at the center. "Basically all the evidence was in our hands, and we wanted to get the evidence back to investigators in a timely manner so they could do their jobs."

The Defense Cyber Crime Center, which has 328 people to assist in computer crime investigations, is seeking to pick up speed in child pornography cases through the use of a new software tool developed under the military's Project KIDS (Known Image Database Systems) initiative.

The tool automates analysis through a hashing technique that finds both known and possible child pornography in data files.

The tool also looks for malware, such as backdoors or Trojans, that might indicate the PC was subverted to download child pornography without the PC user's knowledge.

Currently, the center has approved more than 300 tools for computer forensics purposes in the military. The three primary tools are EnCase from Guidance Software, the Forensic Toolkit from AccessData and iLook, a tool originally developed by Scotland Yard, which is licensed in the U.S. by the Internal Revenue Service only to government users.