US secret intelligence budget files provided by National Security Agency (NSA) whistleblower Edward Snowden show that NSA had warned in 2012 that it planned to investigate up to 4,000 reports of possible internal security breaches.

NSA’s concerns about insider threats were aimed at “anomalous behavior” of agency employees with access to top secret data. The account cited NSA concerns about “trusted insiders who seek to exploit their authorised access to sensitive information to harm US interests.”

The NSA concerns were outlined in top secret documents provided to the Senate and House intelligence committees in February 2012, well before Snowden emerged this summer as the sole source of massive new disclosures about the agency’s surveillance operations.