Facebook has adopted PhotoDNA, Microsoft-made image tracking software, in order to prevent child pornography from being uploaded to the social network.

Facebook is a hugely controlled environment, but with over 6 billion photos uploaded each month, such photos inevitably slip through the net – and Zuckerberg and co are intent on stamping them out.

PhotoDNA was developed by Microsoft specifically for the purpose of tracking down images of child abuse, and Facebook will put the system to work later this week.

Hashing robustly

It works by "robust hashing" – analysing and recording the unique characteristics of each image (its DNA), assigning a unique code ('hash') to them and matching this to other instances of the same image, even if it has been cropped or altered.

Because each photo's DNA is relatively small, the software can sift through billions of images very quickly, and remove any bad ones.

Unfortunately this does mean that only known images can be tracked down; original imagery will continue to rely on other Facebook users reporting them to the site moderators.

But since Microsoft donated the PhotoDNA tech to the National Center for Missing and Exploited Children in 2009, around 10,000 images can now be searched for, with more being added all the time – a fact that's more bad than good.

Via The New York Times