Google and Microsoft have introduced software that makes it harder for users to search for child abuse material online, the companies said in a joint announcement Monday.
Writing ahead of a British summit on Internet safety, Google's executive chairman Eric Schmidt said his company has fine-tuned Google Search to clean up results for over 100,000 search terms. When users type in queries that may be related to child sexual abuse, they will find no results that link to illegal content.
"We will soon roll out these changes in more than 150 languages, so the impact will be truly global," Schmidt wrote in the Daily Mail newspaper.
The restrictions are being launched in Britain and other English-speaking countries first. Similar changes are being brought out on Microsoft's Bing search engine.
The two companies are sharing picture detection technology to identify child abuse photographs whenever they appear on their systems, and Google is also testing technology to identify and remove illegal videos.
Other measures include warnings at the top of Google search for more than 13,000 queries to make it clear that child abuse is illegal.
Schmidt acknowledged that no algorithm is perfect and Google cannot prevent pedophiles adding new images to the web.
Campaigners welcomed the move but doubted how much impact the changes would bring. Pedophiles tend to share images away from public search engines, they say.
"They don't go on to Google to search for images," said Jim Gamble, the former chief of Britain's Child Exploitation and Online Protection Center. "They go on to the dark corners of the Internet on peer-to-peer websites."
British Prime Minister David Cameron agreed there is more to be done, and said the next step was to go after the "dark net," where people secretly share images away from the public search engines.
His government announced Monday that its National Crime Agency is joining forces with the FBI to target pedophiles who use encrypted networks online.
