The IWF's hash list will make it easier to identify illegal images and harder to upload them

Digital fingerprint list pinpoints child abuse images online

Unique digital fingerprints will help Internet firms uncover and remove millions of online images of child sexual abuse.

Every image anti-abuse organisation The Internet Watch Foundation (IWF) come across is allocated a unique 'hash' code that makes it easier to quickly identify and track a duplicate of the image.

Now the charity has decided to share its 'hash list' with tech giants Google, Microsoft, Facebook, Twitter and Yahoo - all IWF members - to help them speed up the identification and removal of illegal content, preventing images from being repeatedly shared.

The move could even help prevent images of abuse from being uploaded to the Internet in the first place by giving companies the power to identify suspect images as they are posted by users.

Chief executive Susie Hargreaves said: "The IWF Hash List could be a game-changer and really steps up the fight against child sexual abuse images online. This is something we have worked on with our members since the Prime Ministers' #WePROTECT summit last December.

"We'll soon be able to offer the hash list to all IWF members, who are based around the world. It means victims' images can be identified and removed more quickly and we can prevent known child sexual abuse images from being uploaded to the internet in the first place."

The IWF is creating hashes using three different technologies: PhotoDNA (developed by Microsoft), MD5 and SHA-1. PhotoDNA can pick up on very similar images such as those that have been cropped or edited, while the other two are open-source cryptographic hashes, which can only be used to identify identical images.

Hashes will be created from images that IWF analysts have assessed, regardless of whether they were sourced from a public report; a report from the online industry; an image actively found by the charity's analysts, or an image from the Home Office's new Child Abuse Image Database.

IWF analysts can find and remove roughly 500 URLs containing child sexual abuse material every day, with each URL containing potentially thousands of images. By hashing all the child sexual abuse images found on each URL, the size and impact of the list should increase rapidly, the IWF says.

Eventually, the charity plans to roll out the list to all eligible members, which includes companies providing services such as the uploading, storage or search of images, filtering or hosting services and social media and chat services, as well as those working in connectivity and data centres.

An NSPCC spokesman said: "This latest development will help tighten the grip on the source of child abuse images but there is still a way to go before we can strangle the life out of this sordid trade.

"This technological breakthrough is really positive and should enable the industry to take a far more pro-active role in blocking these horrendous pictures.

"However, we mustn't forget the victims who may need protection from further abuse. Greater efforts have to be made to arrest those responsible for these abhorrent crimes. Until we have a unified approach to this problem it will continue to plague our communities."

The IWF said it is also working closely with one of its members to trial video hashing software and it hopes to offer the service in the near future.

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