Major U.S. Internet firms have joined an effort to curb the spread of images of sex abuse of children, organizers said Monday, Aug 10.

The Internet Watch Foundation said Facebook, Google, Microsoft, Twitter and Yahoo have agreed to adopt a system to identify and block images of child sex abuse, NDTV Gadgets reports.

The British-based group said in a statement that the system is based on a digital fingerprint, or "hash," which its analysts assign to inappropriate images.

This enables websites participating in the project to filter and block the content.

The "hashes" will be created from images that have been analysed and classified as abusive by analysts from the foundation.

The new system "could be a game-changer and really steps up the fight against child sexual abuse images online," said Susie Hargreaves, chief executive of the IWF, according to the website.

"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."