U.S. Department of Homeland Security

The U.S. Department of Homeland Security has customized its Predator drones, originally built for overseas military operations, to carry out at-home surveillance tasks that have civil libertarians worried: identifying civilians carrying guns and tracking their cell phones, government documents show.

The documents provide more details about the surveillance capabilities of the department's unmanned Predator B drones, which are primarily used to patrol the United States' northern and southern borders but have been pressed into service on behalf of a growing number of law enforcement agencies including the FBI, the Secret Service, the Texas Rangers, and local police.

Homeland Security's specifications for its drones, built by San Diego-based General Atomics Aeronautical Systems, say they "shall be capable of identifying a standing human being at night as likely armed or not," meaning carrying a shotgun or rifle. They also specify "signals interception" technology that can capture communications in the frequency ranges used by mobile phones, and "direction finding" technology that can identify the locations of mobile devices or two-way radios.

The Electronic Privacy Information Center obtained a partially redacted copy of Homeland Security's requirements for its drone fleet through the Freedom of Information Act and published it this week. CNET unearthed an unredacted copy of the requirements that provides additional information about the aircraft's surveillance capabilities.

U.S. Department of Homeland Security

Concern about domestic use of drones is growing, with federal legislation introduced last month that would establish legal safeguards, in addition to parallel efforts underway from state and local lawmakers. The Federal Aviation Administration recently said that it will "address privacy-related data collection" by drones.

The prospect of identifying armed Americans concerns Second Amendment advocates, who say that technology billed as securing the United States' land and maritime borders should not be used domestically. Michael Kostelnik, the Homeland Security official who created the program, told Congress that the drone fleet would be available to "respond to emergency missions across the country," and a Predator drone was dispatched to the tiny town of Lakota, N.D., to aid local police in a dispute that began with reimbursement for feeding six cows. The defendant, arrested with the help of Predator surveillance, lost a preliminary bid to dismiss the charges.

"I am very concerned that this technology will be used against law-abiding American firearms owners," says Alan Gottlieb, founder and executive vice president of the Second Amendment Foundation. "This could violate Fourth Amendment rights as well as Second Amendment rights."

Homeland Security's Customs and Border Protection agency declined to answer questions about whether direction-finding technology is currently in use on its drone fleet. A representative provided CNET with a statement about the agency's unmanned aircraft systems (UAS) that said signals interception capability is not currently used:

U.S. Customs and Border Protection is not deploying signals interception capabilities on its UAS fleet. Any potential deployment of such technology in the future would be implemented in full consideration of civil rights, civil liberties, and privacy interests and in a manner consistent with the law and long-standing law enforcement practices. CBP's UAS program is a vital border security asset. Equipped with state-of-the-art sensors and day-and-night cameras, the UAS provides real-time images to frontline agents to more effectively and efficiently secure the nation's borders. As a force multiplier, the UAS operates for extended periods of time and allows CBP to safely conduct missions over tough-to-reach terrain. The UAS also provides agents on the ground with added situational awareness to more safely resolve dangerous situations.

During his appearance before the House Homeland Security committee, Kostelnik, a retired Air Force major general who recently left the agency, testified that the drones' direction-finding ability is part of a set of "DOD capabilities that are being tested or adopted by CBP to enhance UAS performance for homeland security." CBP currently has 10 Predator drones and is considering buying up to 14 more.

If the Predator drones were used only to identify smugglers or illegal immigrants crossing the Mexican and Canadian borders, or for disaster relief, they might not be especially controversial. But their use domestically by other government agencies has become routine enough -- and expensive enough -- that Homeland Security's inspector general said (PDF) last year that CBP needs to sign agreements "for reimbursement of expenses incurred fulfilling mission requests."

"The documents clearly evidence that the Department of Homeland Security is developing drones with signals interception technology and the capability to identify people on the ground," says Ginger McCall, director of the Open Government Project at the Electronic Privacy Information Center. "This allows for invasive surveillance, including potential communications surveillance, that could run afoul of federal privacy laws."

A Homeland Security official, who did not want to be identified by name, said the drones are able to identify whether movement on the ground comes from a human or an animal, but that they do not perform facial recognition. The official also said that because the unarmed drones have a long anticipated life span, the department tries to plan ahead for future uses to support its border security mission, and that aerial surveillance would comply with the Electronic Communications Privacy Act and other applicable federal laws.

The documents show that CBP specified that the "tracking accuracy should be sufficient to allow target designation," and the agency notes on its Web site that its Predator B series is capable of "targeting and weapons delivery" (the military version carries multiple 100-pound Hellfire missiles). CBP says, however, that its Predator aircraft are unarmed.

Gene Hoffman, a Silicon Valley entrepreneur who's the chairman of the Calguns Foundation, said CBP "needs to be very careful with attempts to identify armed individuals in the border area" when aerial surveillance touches on a constitutional right.

"In the border area of California and Arizona, it may be actively dangerous for the law-abiding to not carry firearms precisely due to the illegal flow of drugs and immigrants across the border in those areas," Hoffman says.

CBP's specifications say that signals interception and direction-finding technology must work from 30MHz to 3GHz in the radio spectrum. That sweeps in the GSM and CDMA frequencies used by mobile phones, which are in the 300MHz to 2.7GHz range, as well as many two-way radios.

The specifications say: "The system shall provide automatic and manual DF of multiple signals simultaneously. Automatic DF should be able to separate out individual communication links." Automated direction-finding for cell phones has become an off-the-shelf technology: one company sells a unit that its literature says is "capable of taking the bearing of every mobile phone active in a channel."

Although CBP's unmanned Predator aircraft are commonly called drones, they're remotely piloted by FAA-licensed operators on the ground. They can fly for up to 20 hours and carry a payload of about 500 lbs.