In the two previous parts of this series, we mainly focused on land-based dangers to people's privacy. However, sometimes danger lurks from above...

As unmanned aerial vehicles (UAVs, or simply drones) have been entering the mass market, many people came to realize that these little machines can make perfect spy vehicles. They're cheap, easy and fast to manufacture, available everywhere, can carry cameras and other equipment and fly high.

And if you think that anyone could see them because of their weird, unnatural shapes or hear them buzzing, you might be far from truth. There are already drones with bird-like designs, which, from high enough, also become completely inaudible.

Flappy Bird: Spy Edition

As soon as several days ago, there was a very peculiar drone that made the news. One that was intentionally designed to look like a predatory bird. And it even has flappy wings!

Bird-shaped drone from Mogadishu, Somalia

This UAV fell from the sky or was somehow downed in Mogadishu, Somalia. Judging by its design and location, we can make a pretty safe bet it didn't fly around for fun. Clearly, someone used it for surveillance. Local reports associate this drone with Somalia’s National Intelligence and Security Agency (NISA)

If you're too far away from Somalia to care about it, here's another spy drone that might be flying in the U.S. skies as you ready this. Again, disguised as a bird. The Maverick, developed by Prioria Robotics for the U.S. Army Special Ops. Of course, it has a camera and you can't hear it when it flies high enough.

Part of the threat in drones lies in their ability to be combined with other technology, including HD cameras, night vision, thermal imaging, laser radar, license plate readers, directional amplifiers, and even IMSI catchers. The possibilities are endless!

Laws!? What laws?...

On top of that, in many countries and states legislation has fallen behind technology and UAVs could be deployed over neighborhoods and streets, watching over way too many people.

While these unmanned aerial vehicles are becoming more commonly used by police, the awareness of the threat they pose to privacy is growing as well. Organizations, such as the American Civil Liberties Union (ACLU) and the Electronic Frontier Foundation (EFF), have been leading the charge against the overuse of drone surveillance.

Law enforcement proponents argue that there is little difference between having a license plate reader and cameras on lampposts through a city and employing a drone with the same technology. After all, both can be used to track a vehicle (in the case of lampposts, by aggregating data from several locations to determine speed and direction).

The increasing sophistication of technology is a unique threat to privacy, that's for sure.

"Drones are smaller, can fly longer, and can be built more cheaply than traditional aircraft,"

points out Richard M. Thompson II, Legislative Attorney at the Congressional Research Service (CRS), in a 2013 report on drones in domestic surveillance operations in the U.S.

Keep calm and carry on via laser recharging

Did you know that Lockheed Martin and LaserMotive have developed a drone that can be recharged from the ground by a laser and stay aloft for over 48 hours? Well, now you know! It's called Stalker UAS (Unmanned Aerial System). The drone has been used by Special Operations Forces since 2006 to perform intelligence, surveillance and reconnaissance missions with a standard flight time of 2+ hours, while its laser recharging system was successfully tested in 2012.

Stalker UAS laser recharger by LaserMotive

"The Stalker UAS was modified for the indoor flight test to incorporate LaserMotive’s proprietary system that makes it possible to wirelessly transfer energy over long distances using laser light to provide a continual source of power to the UAS. At the conclusion of the flight test, held in a wind tunnel, the battery on the Stalker UAS had more energy stored than it did at the beginning of the test," Lockheed Martin announced in July 2012.

As the technology evolves, some believe such a drone could potentially fly forever (with continual recharging). This means that a drone can conceivably monitor a given person's movements with pinpoint accuracy for days or weeks at a time, or, if carrying an IMSI catcher, could monitor the telecommunications in a given territory for an extended period.

Just for fun, you could also check out the Drone Survival Guide. Because that's how worried some people are.

So, there you have it, part 3 of our series on the biggest privacy concerns today. In case you missed the first two parts, here are links to them: mobile devices (part 1) and environmental surveillance (part 2).