Software giant Microsoft is rolling out a free cloud version of its PhotoDNA service, to help law enforcement services and websites detect illegal images including those depicting child sexual abuse from massive photo libraries.

Launched in 2009, PhotoDNA was developed by Microsoft in collaboration with Dartmouth College and it has helped over 70 companies like Facebook and Twitter identify illegal photos for removal but it required substantial time, money and expertise to run it.

The new PhotoDNA Cloud Service is easier to set up and deploy from Microsoft’s Azure platform and businesses can sign up to use it for free.

It works by taking known child sex abuse photos from organizations like the National Center for Missing and Exploited Children (NCMEC) and converting them into numerical values, which function as their fingerprints.

The system can then scour a website for matches and identify even images that were slightly altered, resized or marked to bypass lesser but similar technologies.

Canadian mobile chat network Kik, which has over 200 million users, uses PhotoDNA to detect exploitive profile pictures as they are being uploaded so that they can be removed and the user’s account can be reported to law enforcement agencies.

Microsoft has enhanced the algorithm used to identify illegal images making PhotoDNA 1,000 times faster than previous versions.