Silicon Valley is trying to cleanse the Internet of child pornography

Facebook, Google, Twitter, Yahoo and Microsoft will take a new step toward combating the spread of child pornography, by blocking images identified in partnership with an industry group. The companies will block images of child sexual abuse that have been identified by the Internet Watch Foundation, a U.K.-based nonprofit that aims to locate and stamp out such content online. The effort is aimed at speeding up the identification and removal of images of child sexual abuse worldwide, and preventing them from being uploaded in the first place. Only known child sexual abuse images identified by the IWF will be blocked. Each company will download a list of images that have been “hashed” by IWF analysts, under a process that creates a digital fingerprint of each image. The hashes are created from images that IWF’s analysts have assessed, which come from various online sources like reports from the public, and the U.K.’s Child Abuse Image Database. Hashing the images is designed to make it easier for sites to identify them quickly amid vast amounts of other content.