 Dropbox has been the subject of criticism and controversy related to multiple incidents, including a June 2011 authentication problem that let accounts be accessed for several hours without passwords, a July 2011 Privacy Policy update with language suggesting Dropbox had ownership of users' data, concerns about Dropbox employee access to users' information, July 2012 email spam with recurrence in February 2013, leaked government documents in June 2013 with information that Dropbox was being considered for inclusion in the National Security Agency's PRISM surveillance program, a July 2014 comment from NSA whistleblower Edward Snowden criticizing Dropbox's encryption keys being available to employees, the leak of 68 million account passwords on the Internet in August 2016, and a January 2017 accidental data restoration incident where years-old supposedly deleted files reappeared in users' accounts.The Dropbox headquarters, located in San Francisco, were originally on Market Street, until its expansion to the China Basin Landing building in July 2011, allowing for a significant space increase.As the number of employees grew, the company again needed expansion, and in February 2014, it signed a lease for two buildings in Brannan Street.