Iraq attack shows deadly potential of 'off-the-shelf' drones
You could call it a demonstration of the proliferation of drone use with frightening possibilities.
Last week's attack in northern Iraq in which a small drone exploded killing two Peshmerga fighters and badly wounding two members of the French special forces, marks something of an innovation in modern warfare.
The US launched the first armed drone attack back in October 2001. Since then the use of armed drones has been the preserve of the most sophisticated military actors in the world.
Israel and the US had the early technological lead with Russia and China rapidly developing their own drone industries. Modern military drones can operate over huge distances and remain aloft for extended periods.
They have become an invaluable means of gathering intelligence and conducting surveillance. Their armed counterparts can strike with an array of precision-guided weapons. That is, if you like, the high-end of drone technology.
'Off-the-shelf' terror tool
But as cheaper drones have become available on the high street for amateur photographers and enthusiasts, so the technology has been used by militant groups as well.
So-called Islamic State (IS) and groups like the formerly-named Nusra Front (with close links to al-Qaeda) have been using cheap off-the-shelf drones for some time for surveillance purposes or to shoot propaganda videos. But now they are turning them into weapons.
The exact details of last week's lethal attack in northern Iraq are still unclear. Some reports suggest that the drone exploded as it was being dismantled. It is not clear if these are simply flying booby-traps; other reports suggest that on a separate occasion one was crashed into a building which then exploded.
This is a long way from the sophisticated weaponry deployed daily by the Americans and some of their allies. Indeed the small commercial drones cannot carry much of a pay-load, so their destructive potential is limited, but they clearly can kill, as last week's incident shows.
US troops in the region have been warned to take cover when small drones are observed - up to now they have been regarded as relatively harmless. This kind of weaponised commercial drone is expected to figure in the IS defence of Mosul, though there are no clear estimates of how many of these drones they may have purchased.
How to disarm a drone?
There have been a variety of technical responses to this new drone threat, which alarms police and security officials even more than commanders on the battlefield. Relatively cheap commercial drones are now on sale almost everywhere and anything that can carry a small camera can carry a small explosive device.
Countering this new drone threat involves two main approaches. One is to try to shoot it down or capture it in some way. The other is to interfere with the signals by which it is guided to its intended target.
An anti-drone rifle was spotted in an American position in Iraq earlier this year. The device is called the Drone Defender. It works by disrupting the drone's guidance signal and it looks like a standard military rifle but with two antennae projecting from the front.
The advantage of this type of system - especially for police or security applications - is that it is non-kinetic, in other words it does not send bullets or shells up into the sky, which would clearly be impossible in anything other than a war zone.
Other defensive systems seek to take over control of a drone by cyber means, while others take a more direct route - one manufacturer has even developed a projectile that captures the drone - like spider-man - in a weighted mesh net.
'Drone genie is out of the bottle'
What is alarming is that this new threat has come as something of a surprise. It has been widely predicted by both security officials and military futurologists. There have long been fears that major sporting events, like the last European football championships in France for example, or indeed any major public event - could become the target for a terrorist using some kind of easily-available drone.
And while technologies are available to counter these "improvised flying explosive devices" they are probably not yet reliable enough or available in sufficient numbers. As ever, for now, the attackers may have a temporary advantage as the defenders struggle to catch up.
That of course does not apply in the world of sophisticated military drones where the US and the West in general has a huge advantage. But this is changing too. The US is exporting the weapons to some of its allies.
China too is becoming an exporter of armed drones. And efforts to try to draw up some kind of international treaty to govern the sale and spread of these weapons have so far foundered.
Indeed the proliferation of these weapons is going in two ways - at the top-end of the market sophisticated military systems are spreading relatively quickly and at the bottom-end guerrilla groups, terrorists, drug cartels and so on are beginning to use less sophisticated drones for a variety of purposes.
The drone genie is clearly out of the bottle. As online retailers make plans for the widespread delivery of packages by drone, it is easy to see how those with malign intentions could use the self-same technology for deadly purposes.