Facebook deploys PhotoDNA to scan for
child abuse material - 6/3/2011
Facebook has deployed image-matching technology
PhotoDNA to scan users’ photos for evidence of child
exploitation. The social network announced last Friday
that it would use the hashing technology to prevent child
abuse material from being uploaded and distributed by users.
“We intend to put that technology to use against between
two and three hundred million photo images that are
uploaded every day,” Facebook assistant general counsel
Chris Sonderby said.“The technology will allow us to block
their upload, prevent their distribution and the re-victimization
of the children who are depicted in those images, and also allow us
to refer and report those incidences to law enforcement so they can
take immediate action.”
PhotoDNA was developed by Microsoft and Dartmouth College
in 2009 and relied on a database of sexual abuse images from the
US National Center for Missing and Exploited Children
(NCMEC). The technology calculated and compared digital
signatures, or hash values, of images to identify matches even if the
photos were resized or altered. According to Dartmouth computer
scientist Hany Farid, PhotoDNA analyzed one image in four
milliseconds and detected 99.7 percent of matches in tests.
It had a false positive rate of between one in two billion and one in
ten billion, Farid said, noting that it had not falsely identified a
single image in the two billion MSN images scanned.“It is a very
efficient technology; it will not slow down the general use of the
network,” he said.
Bill Harmon, associate general counsel of Microsoft’s Digital
Crimes Unit, said Microsoft had removed 1,000 images from its
SkyDrive cloud storage service since February, based on 4,000
NCMEC signatures. Microsoft also compared Bing image search
indexing against 10,000 NCMEC signatures, and had identified
1,500 addresses of online child exploitation images to date.
NCMEC president and CEO Ernie Allen said Microsoft’s
PhotoDNA beta tests had led to arrests in New Zealand. He
hoped to establish partnerships with more online services,
especially those that enabled social media and photo sharing.