Traces of guilt

By John Leyden

9th November 2009 11:46 GMT

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Innocent people have been branded as child abusers after malware infected their PCs, an AP investigation has discovered.

Technically sophisticated abusers sometimes store images of child abuse on PCs infected by Trojans that grant them illicit access to compromised machines.

The plight of those framed in this way is all the worse because paedophiles commonly use supposed malware infections of their PCs to explain the presence of images of child abuse. Because of this the "Trojan did it" defence is understandably met with scepticism from law enforcement professionals.

"It's an example of the old `dog ate my homework' excuse," says Phil Malone, director of the Cyberlaw Clinic at Harvard's Berkman Center for Internet & Society told AP. "The problem is, sometimes the dog does eat your homework."

AP interviewed former child abuse suspects who were arrested after depraved images were found on their computers, as well as police and computer forensic experts.

Michael Fiola, a former Massachusetts government worker, was arrested two years ago after child abuse images were discovered on his state-issued laptop computer after officials became suspicious of huge data use bills associated with the machine and began an investigation. He was eventually cleared nearly 11 months later after defence experts were able to show that the laptop harboured malware programmed to visit as many as 40 child porn sites per minute, far faster than a human surfer would be able to accomplish.

Forensics experts hired by the prosecution agreed with these findings and the case, which had nearly ruined Fiola's life, was dropped.

Fiola was fired from his job before enduring death threats and losing friends. His wife stood by him, however, and the couple were able to raise a $250,000 legal defence fund after selling their car, cashing in their savings and re-mortgaging their home. "It ruined my life, my wife's life and my family's life," Fiola told AP.

A cap on the amount of damages they might receive has effectively prevented the Fiolas from suing the state.

Child abuse webmasters sometimes use either compromised consumer or business systems as a warehouse for child abuse images and videos. Paedophile images can also land on systems as the result of a nasty prank or as an act of deliberate sabotage.

Two UK men were cleared of child-abuse offences in 2003 after it was shown that computer viruses were behind the presence of child abuse images on their PCs. One of the PCs was infected by a virus that changed the home page of the Windows machine to a child porn site. The other man's machines was infected by a virus that downloaded images of child abuse.

One of the two unnamed men lost custody of his seven-year-old daughter and spent a week in jail on remand because of the case.

In another case Chris Watts, a British computer forensics expert, helped clear a hotel manager whose colleagues found child porn on a shared workplace PC. The manager had been looking for ways to download pirated computer games when his web session was redirected to a child abuse site.

More details on the cases and discussion of the issue can be found here.

Scientists in Israel have demonstrated that it is possible to fabricate DNA evidence, undermining the credibility of what has been considered the gold standard of proof in criminal cases.

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The scientists fabricated blood and saliva samples containing DNA from a person other than the donor of the blood and saliva. They also showed that if they had access to a DNA profile in a database, they could construct a sample of DNA to match that profile without obtaining any tissue from that person.

“You can just engineer a crime scene,” said Dan Frumkin, lead author of the paper, which has been published online by the journal Forensic Science International: Genetics. “Any biology undergraduate could perform this.”

Dr. Frumkin is a founder of Nucleix, a company based in Tel Aviv that has developed a test to distinguish real DNA samples from fake ones that it hopes to sell to forensics laboratories.

The planting of fabricated DNA evidence at a crime scene is only one implication of the findings. A potential invasion of personal privacy is another.

Using some of the same techniques, it may be possible to scavenge anyone’s DNA from a discarded drinking cup or cigarette butt and turn it into a saliva sample that could be submitted to a genetic testing company that measures ancestry or the risk of getting various diseases. Celebrities might have to fear “genetic paparazzi,” said Gail H. Javitt of the Genetics and Public Policy Center at Johns Hopkins University.

Tania Simoncelli, science adviser to the American Civil Liberties Union, said the findings were worrisome.

“DNA is a lot easier to plant at a crime scene than fingerprints,” she said. “We’re creating a criminal justice system that is increasingly relying on this technology.”

John M. Butler, leader of the human identity testing project at the National Institute of Standards and Technology, said he was “impressed at how well they were able to fabricate the fake DNA profiles.” However, he added, “I think your average criminal wouldn’t be able to do something like that.”

The scientists fabricated DNA samples two ways. One required a real, if tiny, DNA sample, perhaps from a strand of hair or drinking cup. They amplified the tiny sample into a large quantity of DNA using a standard technique called whole genome amplification.

Of course, a drinking cup or piece of hair might itself be left at a crime scene to frame someone, but blood or saliva may be more believable.

The authors of the paper took blood from a woman and centrifuged it to remove the white cells, which contain DNA. To the remaining red cells they added DNA that had been amplified from a man’s hair.

Since red cells do not contain DNA, all of the genetic material in the blood sample was from the man. The authors sent it to a leading American forensics laboratory, which analyzed it as if it were a normal sample of a man’s blood.

The other technique relied on DNA profiles, stored in law enforcement databases as a series of numbers and letters corresponding to variations at 13 spots in a person’s genome.

From a pooled sample of many people’s DNA, the scientists cloned tiny DNA snippets representing the common variants at each spot, creating a library of such snippets. To prepare a DNA sample matching any profile, they just mixed the proper snippets together. They said that a library of 425 different DNA snippets would be enough to cover every conceivable profile.

Nucleix’s test to tell if a sample has been fabricated relies on the fact that amplified DNA — which would be used in either deception — is not methylated, meaning it lacks certain molecules that are attached to the DNA at specific points, usually to inactivate genes.

Sign in to Recommend Next Article in Science (4 of 24) » A version of this article appeared in print on August 18, 2009, on page D3 of the New York edition.