The US military has fixed a problem that allowed Iraqi militants to use cheap software to intercept the video feeds of US-operated drones, a defense official said on Thursday.

"This is an old issue that's been addressed," the official, who spoke on condition of anonymity, told reporters. The problem has been "taken care of," he said.

Pentagon officials sought to play down security concerns with US drones after the Wall Street Journal reported that Iranian-backed Shiite insurgents had used software programs such as SkyGrabber -- available online for 25.95 dollars (18 euros) -- to capture live video footage from the unmanned aircraft.

The defense official confirmed the report was accurate but would not discuss details of efforts to encrypt the link between drones and operators on the ground.

Some sensitive video feeds from drones are routinely encrypted, another defense official, who asked not to be named, told AFP. But the extent of the encryption remained unclear.

James Clapper, the undersecretary of defense for intelligence, reviewed the problem on orders from Defense Secretary Robert Gates and concluded the hacking by Iraqi insurgents revealed a flaw in the security of the drone fleet, the Journal reported.

The Defense Department said in a statement that it "constantly evaluates and seeks to improve the performance and security of our various" drone systems.

"As we identify shortfalls, we correct them as part of a continuous process of seeking to improve capabilities and security. As a matter of policy, we don't comment on specific vulnerabilities or intelligence issues," it said.

The case exposed a possible weakness with the highly valued drones, which are increasingly crucial to US military operations in Afghanistan and Iraq as well as CIA manhunts against Al-Qaeda figures in Pakistan.

The Pentagon is deploying more armed and unarmed drones to Afghanistan to back up a surge of US forces there, and Gates has placed a high priority on expanding and improving the fleet of unmanned aircraft.

There was no evidence that militants could control the drones or otherwise interfere with their flights, but the vulnerability would allow the unmanned craft to be monitored and tracked.

The problem was uncovered in July 2009, when the US military found files of intercepted drone video feeds on the laptop of a captured militant, intelligence and defense officials told the Journal.

They discovered "days and days and hours and hours of proof," an unnamed source told the Journal. "It is part of their kits now."

Some of the most detailed examples of drone intercepts have been uncovered in Iraq, but the same technique is known to have been employed in Afghanistan and could easily be used in other areas where US drones operate.

The US government has known about the flaw since the 1990s, but assumed its adversaries would not be able to take advantage of it, the Journal said.

Adding encryption to a decade-old system requires upgrading several components of the system linking drones to ground control.

One of the developers of SkyGrabber, which is made by Russian company SkySoftware, told the Journal he had no idea the program could be used to intercept drone feeds.

"It was developed to intercept music, photos, video, programs and other content that other users download from the Internet -- no military data or other commercial data, only free legal content," Andrew Solonikov told the Journal.

The report on intercepted drone feeds came a day after Lieutenant General David Deptula, Air Force deputy chief of staff for intelligence, surveillance and reconnaissance, told reporters that some unmanned aircraft in Afghanistan soon would be equipped with a new hi-tech camera system called "Gorgon Stare" -- allowing a drone to beam back at least 10 separate video feeds at the same time.

Earlier Thursday, two separate missile strikes by US drones killed at least 14 militants in northwest Pakistan, security officials there said.