MUSCULAR (DS-200B) is a National Security Agency (NSA) surveillance program that was exposed in 2013 by Edward Snowden. The program was designed to intercept and collect data from the fiber optic cables that connect Google’s and Yahoo’s data centers around the world. The data collected by MUSCULAR included email, search queries, and other sensitive information. The program was run jointly with the British intelligence agency, Government Communications Headquarters (GCHQ). The exposure of MUSCULAR and other NSA surveillance programs sparked a global debate about the balance between national security and privacy.

MUSCULAR was part of a larger NSA surveillance program called OAKSTAR, which was focused on collecting foreign intelligence from various sources. The MUSCULAR program was specifically designed to target the data centers of Google and Yahoo, which are among the largest in the world and handle vast amounts of data. It is not clear how much data the NSA was able to collect through MUSCULAR, but the program was considered to be a major intelligence coup.

The exposure of MUSCULAR and other NSA surveillance programs led to widespread concern about the extent of government surveillance and the potential for abuse. Many privacy advocates argued that the programs violated the Fourth Amendment to the US Constitution, which protects citizens from unreasonable searches and seizures. The revelations also led to calls for greater transparency and oversight of intelligence agencies.