While working for U.S. intelligence agencies, Edward Snowden had another secret identity: an online commentator who anonymously railed against citizen surveillance and corporate greed. Throughout the eight years that Snowden worked for the Central Intelligence Agency and National Security Agency contractors, he posted hundreds of messages on a public Internet forum under a pseudonym. "I can't hope to change the way things are going by overtly complaining, writing letters, or blowing things up," Snowden wrote in 2003 in response to a discussion about corporate greed on the Ars Technica online forum. Snowden was employed by an unidentified classified agency in...