MUSCULAR (DS-200B), located in the United Kingdom, is the name of a surveillance program jointly operated by Britain's Government Communications Headquarters (GCHQ) and the U.S. National Security Agency (NSA) that was revealed by documents released by Edward Snowden and interviews with knowledgeable officials. GCHQ is the primary operator of the program. GCHQ and the NSA have secretly broken into the main communications links that connect the data centers of Yahoo! and Google. Substantive information about the program was made public at the end of October 2013.