Just days before China hosts the World Internet Conference, the Chinese government blocked access to several popular websites as they target content delivery networks that serve much of the Internet. An affiliate of Verizon called EdgeCast says censors have taken down several networks that provide local servers to help speed website performance. The online activist group Greatfire.org said Wednesday that it was the target of the Chinese action, which blocked many other sites that use EdgeCast. The group enables Chinese Internet users to access websites otherwise blocked by Chinese censors. China employs thousands of censors who block hundreds of websites and erase social media messages dealing with sensitive political topics. At the same time, it claims some of the world's most popular online sites, including e-commerce giant Alibaba.