WASHINGTON -- Militants in Iraq have used $26 off-the-shelf software to intercept live video feeds from U.S. Predator drones, potentially providing them with information they need to evade or monitor U.S. military operations.

Senior defense and intelligence officials said Iranian-backed insurgents intercepted the video feeds by taking advantage of an unprotected communications link in some of the remotely flown planes' systems. Shiite fighters in Iraq used software programs such as SkyGrabber -- available for as little as $25.95 on the Internet -- to regularly capture drone video feeds, according to a person familiar with reports on the matter.

U.S. officials say there is no evidence that militants were able to take control of the drones or otherwise interfere with their flights. Still, the intercepts could give America's enemies battlefield advantages by removing the element of surprise from certain missions and making it easier for insurgents to determine which roads and buildings are under U.S. surveillance.

The drone intercepts mark the emergence of a shadow cyber war within the U.S.-led conflicts overseas. They also point to a potentially serious vulnerability in Washington's growing network of unmanned drones, which have become the American weapon of choice in both Afghanistan and Pakistan.

The Obama administration has come to rely heavily on the unmanned drones because they allow the U.S. to safely monitor and stalk insurgent targets in areas where sending American troops would be either politically untenable or too risky.

The stolen video feeds also indicate that U.S. adversaries continue to find simple ways of counteracting sophisticated American military technologies.

U.S. military personnel in Iraq discovered the problem late last year when they apprehended a Shiite militant whose laptop contained files of intercepted drone video feeds. In July, the U.S. military found pirated drone video feeds on other militant laptops, leading some officials to conclude that militant groups trained and funded by Iran were regularly intercepting feeds.

In the summer 2009 incident, the military found "days and days and hours and hours of proof" that the feeds were being intercepted and shared with multiple extremist groups, the person said. "It is part of their kit now."

A senior defense official said that James Clapper, the Pentagon's intelligence chief, assessed the Iraq intercepts at the direction of Defense Secretary Robert Gates and concluded they represented a shortcoming to the security of the drone network.

"There did appear to be a vulnerability," the defense official said. "There's been no harm done to troops or missions compromised as a result of it, but there's an issue that we can take care of and we're doing so."

Senior military and intelligence officials said the U.S. was working to encrypt all of its drone video feeds from Iraq, Afghanistan and Pakistan, but said it wasn't yet clear if the problem had been completely resolved.

Some of the most detailed evidence of intercepted feeds has been discovered in Iraq, but adversaries have also intercepted drone video feeds in Afghanistan, according to people briefed on the matter. These intercept techniques could be employed in other locations where the U.S. is using pilotless planes, such as Pakistan, Yemen and Somalia, they said.

It was thought that it would be more hassle than it is worth to share keys with ALL of the people who need access to the stream.