Before going ahead with plans to allow the widespread use of unmanned aircraft, or drones, in civilian airspace, lawmakers must do more to protect privacy and reduce the likelihood of sabotage, experts and members of the U.S. Congress told a House committee looking into the issue this week.

Currently, there are about 200 unmanned aerial vehicles, or UAVs, owned by 100 non-government entities like law enforcement agencies and academic institutions, that have been authorized to fly in the U.S., Congressman Michael McCaul, said in his opening statement to the Homeland Security committee's subcommittee on oversight investigations, and management.

McCaul is the chairman of the subcommittee, which held a hearing Thursday on the government's plan to to allow the use of non-military drones nationwide by 2015.

The Federal Aviation Administration has already started expanding the regulations governing the use of drones in national airspace.

To date, the drones had been limited to just a few restricted zones controlled by the military and those wishing to use them had to apply for special "certificates of authorization."

But in May, the FAA began a three-year process of integrating drones into U.S. airspace by allowing police, firefighters and other civilian first-responders to fly UAVs that are no heavier than 11 kilograms.

The next step in the integration is to select six test sites where the FAA will test how safe it is for civilian drones to share airspace with other aircraft.

The FAA estimates that about 10,000 non-military drones will be in use in the U.S. within five years.

GPS hacking a possibility

But this growing interest in unmanned vehicles has raised concerns that the surveillance capabilities of drones could violate people's privacy or that the signals used to guide them could be hacked and the drones diverted to crash into infrastructure or other targets, particularly in heavily populated areas.

Some have also worried that the increasing availability and affordability of drones makes them likely delivery systems for chemical or biological weapons or explosives.

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A model of the EuroHawk drone, built by Northrop Grumman and EADS Defence & Security, at a German army base near Bonn. Military drones are more sophisticated than those used for civilian purposes and cost millions of dollars, compared to as little as $25,000 for civilian UAVs. (Wolfgang Rattay/Reuters)

McCaul referenced a 2011 case in this context in which the FBI uncovered a plot to use small drone-like aircraft laden with explosives to collapse the dome of the U.S. Capitol and attack the Pentagon.

McCaul warned on Thursday that no federal agency is currently charged with examining these issues and that the FAA has so far restricted its regulatory actions to ensuring the new drones don't pose a risk to civilian aircraft but has not tackled the national security and privacy implications of opening up civilian airspace to drones.

"With only two and a half short years until drones begin to dominate the skies in the U.S. homeland, no federal agency is taking the lead to deal with the full implications of using unmanned aerial systems and developing the relevant policies and guidelines for their use," he said. 

McCaul said it's important that the Department of Homeland Security (DHS) come up with a policy on the use of civilian drones and criticized DHS officials for not appearing at Thursday's hearing.

"DHS's lack of attention about this issue is incomprehensible," McCaul said.

He said he might subpoena officials to appear at future hearings on the subject.

Private sector interest growing

To date, the drones have mostly been used by the military and law enforcement agencies or for weather- and other science-related research. Generally, they perform tasks that are too dangerous or tedious for humans or collect data from remote or hard-to-access areas.

But there is growing interest by the private sector to use drones for things such as mapping and surveying in the oil and gas, forestry and utilities sectors, and for crop-dusting in agriculture.

Drones are a cheaper alternative to manned aircraft, and some predict the growing market for them could be worth billions of dollars.

Although specialized military drones can cost  in the tens of millions of dollars, civilian drones can cost as little as $25,000 US.

The Ontario Provincial Police uses drones that cost about $30,000 Cdn each and which the OPP says is much cheaper than leasing planes and helicopters for about $1,000 and $1,600 an hour.

State, provincial and municipal police departments are some of the most interested in expanding their use of drones for everything from surveying crime scenes to patrolling borders and spying on criminals.

Engineers hijack drone

But while military drones use encryption to secure the signals the aircraft use to navigate, civilian drones do not have such protection and are more vulnerable to sabotage.

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A U.S. RQ-170 unmanned spy plane that disappeared in Iran in December 2011 displayed in front of a flag with Persian script denouncing the U.S., Israel and Britain at an unknown location in Iran. Iranian officials said they had hacked the plane's GPS system and forced it to land in Iran. (Handout/Sepah News.ir/Reuters)

Concerns about possible hijacking of civilian drones were raised last month after researchers at the University of Texas at Austin demonstrated that they could hack into the GPS navigational system of a civilian drone and steer it onto a new course.

Homeland Security had asked Cockrell School of Engineering assistant professor Todd Humphreys and his students to try and hack a university-owned drone as a security exercise.

The technique they used is one called spoofing in which false location and time co-ordinates are sent to the drone's GPS receiver, and the drone is guided  onto a new course without ever detecting that anything is wrong.

"I think this demonstration should certainly raise some eyebrows and serve as a wake-up call of sorts as to how safe our critical infrastructure is from spoofing attacks," said Milton R. Clary, an aviation policy analyst with Overlook Systems Technologies who works with the U.S. department of defence to identify and mitigate spoofing attacks.

On Thursday, Humphreys told the House subcommittee that he was worried that drones "could be a weapon in the arsenal of organized crime, or state actors, or organized terrorists."

Military drones also vulnerable

The experiment conducted by Humphreys and his team was not the first example that highlighted the security vulnerabilities of drones.

In December 2011, a U.S. military drone spying on Iran's nuclear infrastructure was downed by Iranian authorities who said they used spoofing to hack into the drone's communications system and fool it into landing in Iran.

Jammers that could disrupt drone GPS signals can be had online for as little as $50 US, Gerald Dillingham of the Government Accountability Office (GAO) told the hearing.

Michael Toscano, president of the Association for Unmanned Vehicles Systems International, said in a written submission to the subcommittee that the industry that builds drones for civilian use "takes the potential for spoofing very seriously and is already advancing technologies ... to prevent it."

With files from The Associated Press