US intelligence plans to introduce a massive system of internal surveillance by electronically monitoring the behavior of up to 5 million federal employees with secret clearances, current and former officials told the Associated Press.

The computerized system would provide continuous monitoring of financial and other databases of government employees, according to officials and documents reviewed by the AP. Speaking before Congress in February, Director of National Intelligence James Clapper said the proposed system would extend "across the government," drawing on "six or seven data streams."

While the Defense Department has had such a system in the works for more than decade, revelations made by NSA Whistleblower Edward Snowden have likely expedited its implementation.

Monitoring of employees at some agencies could begin as early as September and be fully operational across the government by September 2016. The price tag, Clapper conceded, "is going to be costly."

An administration review of the government’s security clearance process, due later this month, is expected to support continuous monitoring along with a raft of other substantive changes. Workers with secret clearances are already required to undergo background checks before being hired and may be subject to future re-investigations if necessary, though Clapper told Congress last month that intermittent checks were insufficient.

"What we need is a system of continuous evaluation where when someone is in the system and they're cleared initially, then we have a way of monitoring their behavior, both their electronic behavior on the job as well as off the job," Clapper said.

The system is expected to cull through multiple sources of information, including private credit agencies, law enforcement databases and threat lists, military and other government records, licenses, data services and public record repositories to spot unusual behavior patterns.

Investigators would then analyze the data along with information gathered from social media and even polygraph tests, officials said on condition of anonymity.

Although the system draws parallels between monitoring systems already in place within the airline and banking industries, it most clearly mirrors the Pentagon’s Automated Continuous Evaluation System (ACES).

The ACES program, designed by researchers from the California-based Defense Personnel and Security Research Center and defense contractor Northrop Grumman, has passed several pilot tests but is not fully operational.

According to project documents, ACES links to up to 40 databases, including previously available government documents, but also information from three major credit agencies.

One former official familiar with ACES said researchers had considered adding records from medical and mental health files, but decided to defer to policy makers as a result of privacy concerns. Research into ACES has so far cost $84 million.

The internal monitoring system would provide a technological component to President Barack Obama’s much maligned Insider Threat Program proposed in July. As part of the initiative, Obama ordered millions of federal employees to report suspicious actions of their colleagues based on suspect behavioral profiling techniques. Federal employees and contractors were asked to monitor co-workers for key 'indicators' that include stress, divorce, financial problems, odd working hours and unexplained travel as means of predicting whether thy might do “harm to the United States."

Last week, outgoing NSA Director Keith Alexander said intelligence, Defense and Cyber Command officials are collaborating on "insider threat" planning, with the Pentagon requesting nearly $9 million next year for its insider threat-related research. The NSA, meanwhile, is already conducting electronic monitoring of agency staffers involved in surveillance operations.

Snowden, a former CIA employee and NSA contractor, last year exposed dragnet global surveillance programs. The leaks exposed the agencies' practices of tapping the internet networks, emails, and phone calls of millions of ordinary citizens at home and abroad.