A new free smart phone app that tracks drone signals close to airports or crowded events could help prevent unmanned aerial vehicles being used for nefarious purposes such as terrorism.

With terror attacks gripping the world in recent years, security experts are seeking new ways of ramping up defense systems. And now, they're calling on you to help.

By downloading a new, free, phone app, users are being encouraged to help keep people at stadiums or airports safe from potential attacks.

DroneWatcher uses a smart phone's wifi receiver to monitor for radio signals of unmanned aerial vehicles (UAVs). The data collected from multiple users' phones is sent automatically to security officials for them to act on.

So as Edward Zakrajsek at the developing company DeTect Global puts it - all you really have to do is download it.

Edward 'Zak' Zakarajsek, General Manager of Detect Global, saying:

"The application is really crowdsourcing, where if we have a hundred users in an area using the app all of their data from detecting that drone gives us much better information, and instead of knowing that the drone is near one phone we can now locate that drone and the controller and essentially plot that drone on a map now with good accuracy and track its movements."

Although the Android-based app is free, developers will be paid by organizers of concerts, sporting venues and airports to access the crowdsourced data.

Last October Turkish warplanes shot down an unidentified drone in Turkish air space near the Syrian border after repeated warnings for it to be diverted were ignored.

And a year earlier an international soccer match in Belgrade between Serbia and Albania was abandoned after a drone carrying a flag depicting so-called Greater Albania, was flown above the pitch and grabbed by a Serbian player.

British security consultant Matthew Finn, managing director of Augmentiq, puts the potential of these drones into perspective.

Matthew Finn, Managing Director of Augmentiq, saying:

"If you've now got control of a device that you could put into a sensitive area you could weaponise it, you could do something with that drone that could cause untold damage in a particular area that you as an individual wouldn't be able to get to … You can get into that football stadium, you can get into that shopping mall, you can get into these other areas."

Finn says law enforcement and security organizations need to think carefully about how to deal with the threat.

With enough users, DroneWatcher could be a step in the right direction.