Mathematical algorithms identifying images based on content are being deployed by U.S. Defense Department examiners and investigators as a key portion of the DOD’s share in the battle against child porn, DOD officials told an Internet crime conference in Florida this week.
The DOD has spent about $500,000 and assigned top cybercrime researchers to fight child porn, but since launching the so-called Known Image Database System (KIDS) last July, department forensic examiners have been smothered by a flood of cases.
That’s what senior Defense forensic examiner Bill Harback told a DOD Cyber Crime Conference, as did the DOD Cyber Crime Center’s executive director, Steven Shirley. Shirley, in fact, said about half the criminal forensic investigations done by the so-called DC3 have involved child porn.
Shirley told the conference the easier availability of computer hard drives, digital cameras, and scanners has driven a swelling of child porn cases – and a broadening of who’s investigating it. "Before the PC, the only people who were concerned with child pornography were customs and the postal inspectors,” Shirley said. “Now it's every police agency.”
DOD contracted with General Dynamics in May 2004 to create the KIDS database of known child porn images, identifiable by message-digest algorithms known as hash sets – alphanumeric values identifying each image based on content, as the program describes them.
According to DOD Computer Forensic Laboratory director, U.S. Air Force Lt. Col. Ken Zatyko, the hash sets are used to compare images on hard drives to known child porn images, leaving investigators to work on other images and data found during a search of suspect material including Web surfing and Net search history.
That, he said, can help investigators determine the computer owner was hunting child porn actively, as well as helping them determine whether malicious code such as Trojan horse programs were used to plant child porn without the owner knowing it.
But the DOD is also said to be rather tight when it comes to letting others use the hash sets. “The problem is,” said Adult Sites Against Child Pornography executive director Joan Irvine, “they will not share these hash values with many other government offices and definitely not businesses to allow them to help.”
ASACP has tried to get approval to use the hash sets to no avail since they went into use last year.
The National Center for Missing and Exploited Children and the FBI have used hash sets and image databases already, but Zatyko said the DOD’s involve newer, more secure algorithms to make hash values more accurate and good for more reliable court evidence.
