No light on the darknet

Having refused for months, Internet firms Google and Microsoft, which owns Bing, say they have listened to calls for them to block child sex abuse search words.

Announcing a raft of measures ahead of a meeting with the British prime minister in London, the two companies said they had reprogrammed their search algorithms to block 100,000 search terms relating to illegal content.

The focus is images of child sex abuse.

Prime Minister David Cameron described the move as "significant progress."

Any impact on the darknet?

The move has been criticized by a number of child protection and Internet experts, who suggest it will have little impact.

In an interview with 'The Telegraph' newspaper, Dr Joss Wright of the Oxford Internet Institute, said "the first thing to remember is that Google is the search engine, not the Internet […] they can't take [illegal content] down from the Internet."

Jim Gamble, a former chief executive of the Child Exploitation and Online Protection Centre and current head of the Ineqe Group, also warns that "pedophiles don't search out their images on the Internet." He's been quoted by "Metro" as saying most traffic in illegal content takes place on peep-to-peer (P2P) networks - on the darknet.

But speaking to DW, John Carr, a top advisor to the British government on the Internet and child protection, welcomed the steps taken by Google and Microsoft.

Carr says this is the start of a "huge experiment."

"I'm pretty sure it will have an impact but we're going to learn," says Carr. "I agree we've got to deal with the darknet as well, but we don't have to do the really difficult stuff first."

You can listen to the full interview above.

Google and Microsoft say the changes have been prepared in more than 150 languages, and warnings will pop-up for 13,000 searches other than the main 100,000 which will be blocked.