Lille (France) (AFP) - Jihadists have yet to shut down a power grid, paralyse a transport network or banking system or take over a key industrial site from afar, but experts say the threat of such a cyber attack should be taken seriously.
Analysts fear that while extremist groups may not have the necessary skills themselves, they could hire someone else to wreak havoc.
"Digital attacks with major impacts are unlikely in the short term," said Guillaume Poupard, head of France's digital security service ANSSI, speaking to AFP at an international cyber security conference in Lille, France.
"However, that could change very fast. Our real fear, and we may already be there, is that they will use mercenaries, people who will do anything for money," Poupard said.
The Islamic State group, Al-Qaeda and other jihadist groups are so far using the internet mainly for propaganda and recruitment purposes.
"The skills are complex, though not at the level of a nuclear weapon," Poupard said.
"With a few dozen people, a little money, but not that much, you can be effective."
Earlier this month, Europol director Rob Wainwright also warned of the use of digital mercenaries by jihadist groups at the World Economic Forum in Davos, Switzerland.
"Even if they don't have access to the capabilities, they can simply buy it on the darknet (a hidden internet realm of encrypted websites), where there is an enormous trade in cyber criminal technology," Wainwright said at a panel discussion on "Terrorism in the Digital Age".
"That said, attacking the critical national infrastructures at least of most countries is... not easily done, and it's something that is not as immediate and showy as firing automatic weapons in a theatre or in public," he added.
Data pirates and cyber criminals from several countries, often linked to organised crime, offer their services on the darknet.
Given the anonymity of the sites, some may help jihadists without realising it.
"In fact, that's our fear," Poupard said. "It's no so much that IS can quickly develop cyberattacks but that they will be able to go through intermediaries."
- Asymmetrical warfare -
Speaking in Davos, retired Pakistani general Raheel Sharif said cyber terrorism is "a real threat".
"As technology improves, the possibility exists that someone can hack into a very sophisticated system and control that resource in such a way as to do maximum damage somewhere."
Most developed countries are steadily boosting their defences against the cyber threat, be it terrorism, crime or espionage.
"Terrorist groups that currently use the internet for planning, propaganda and recruitment purposes could become full players in the cyber arena," French Defence Minister Jean-Yves Le Drian said last month as he unveiled his country's policy on military cyber security.
"Since asymmetrical operations are naturally etched into their DNA, cyber space gives them an obvious field of action, where major damage can be inflicted with limited means," he said.
Disturbing precursors of more insidious actions ahead are internet interlopers that do not steal or destroy data but appear to map websites, preparing offensive weapons for later use.
"This kind of attack has even begun in some countries," Poupard said. "We are closely following what's happening in Ukraine where strange breakdowns are becoming frequent that are caused by extremely sophisticated actions."