Google devises system to rid its service of child abuse pages

Google to clean up results for more than 100,000 search queries and warn users of more than 13,000 queries

Google claims that a 200-strong team that it put together to expunge child abuse pages from its search engine has devised a system that it plans to deploy globally.

The initiative comes ahead of a Child Abuse Summit at 10 Downing Street today and follows stinging criticism from prime minister David Cameron four months ago, who challenged Google and other internet companies to "clean up" their services.

In an article published in today's Daily Mail, Google executive chairman Eric Schmidt defended his company's reputation and outlined the ways in which the company was tackling online child abuse imagery.

"We've fine tuned Google Search to prevent links to child sexual abuse material from appearing in our results. While no algorithm is perfect - and Google cannot prevent paedophiles adding new images to the web - these changes have cleaned up the results for over 100,000 queries that might be related to the sexual abuse of kids," wrote Schmidt.

Furthermore, the new system and policies will be applied globally to more than 150 languages by Google, he said.

However, Schmidt warns that there are no technical means by which the company can definitively identify images of child sex abuse.

"This is because computers can't reliably distinguish between innocent pictures of kids at bathtime and genuine abuse. So we always need to have a person review the images. Once that is done - and we know the pictures are illegal - each image is given a unique digital fingerprint."

Microsoft has shared its image detection software with Google for this purpose.

"Paedophiles are increasingly filming their crimes. So our engineers at YouTube have created a new technology to identify these videos. We're already testing it at Google, and in the new year we hope to make it available to other internet companies and child safety organisations," writes Schmidt.

The company will also second engineers to the Internet Watch Foundation (IWF) in the UK and the National Center for Missing and Exploited Children in the US.

The summit at Downing Street will be attended by representatives from internet service providers BSkyB, TalkTalk, BT and Virgin Media, as well as Google, Microsoft, the National Crime Agency, children's charity the NSPCC and the IWF.

"Google and Microsoft have come a long way," Cameron told the Daily Mail. "A recent deterrence campaign from Google led to a 20 per cent drop off in people trying to find illegal content, so we know this sort of action will make a difference."