Without diminishing the shock of the Bastille Day events, the terrorist's warning had been, sadly, plain to see.

"Run him over with your car," was the bloodthirsty demand almost two years ago from Islamic State, urging its sympathisers to find any means to carry out attacks in the West.

Now a heavy truck has bulldozed a crowd on a promenade in France.

The actual motivations of the driver barely matter. It is not yet clear whether he had a connection to Islamist dogma or not. The terrorists will nevertheless claim him as their own, and will likely look to mimic the awful carnage.

The example could inspire the next attack in Europe, the United States or in Australia.

"We have many measures of controlling traffic," said Mark Briskey, a former Australian Federal Police officer and senior lecturer in terrorism studies at Curtin University when asked how easy it would be to carry out such an attack locally.

"But unless security agencies have specific information to warn about an individual, [an attack] is entirely simple to do."

The Nice attack is not unprecedented. A man in Canada rammed his car into two soldiers in October 2014 after spouting Islamist extremism.

These kinds of acts betray terrorists' weakness, while still inspiring fear.

This attack in Nice at a time of national celebration, understandably leaves people everywhere worried about large crowds.

The French have become a target of opportunity. There, extremists from within Europe's Muslim community are concentrated enough to offer each other succour as they plot attacks. Britain suffered the same fate following the 2005 London bombings until the terrible cycle was broken - as eventually it will be in France and neighbouring Belgium.

In the meantime, community suspicions will grow in Europe, just as the terrorists want.

On Saturday, Fairfax Media publishes the story of an Australian freelance reporter who spent the better part of nine months undercover, carefully ingratiating himself with local extremists professing support for Islamic State. Asked how easily something like the attack in Nice could happen here, he has no hesitation.

"These guys are dangerous. They're adamant on doing something in Australia. And they have the belief," he says.

"I think the question is the capability. Especially with what happened [on] Bastille Day with what was done with the lorry truck, it shows that anyone who wants to do something, they can do it."

"From what I experienced here, all the people talking about doing something on a grand scale or a small scale, they want to make attacks happen."

Sapping the terrorist's motivation is key, but with talk that Islamic State is preparing for the inevitable loss of its strongholds in Syria and Iraq, there is danger the group will further lash out. Security measures can never be perfect.

Many public buildings are surrounded by bollards or carefully position large planters to obstruct vehicles. Parliament House in Canberra saw them installed way back in 1992 after a man crashed his four-wheel drive into the front doors in a protest that seemed almost quaint at the time. Had it happened today, it would spark catastrophic alarm.

Yet when one target is made more difficult to strike, the terrorists have proved adept at finding the next.

The shock of September 11, 2001, was to deliberately crash airliners into buildings, an act unimaginable until viewed with hindsight, when it seemed an obvious threat.

Protections for society have improved in the years since, but those who intend to sow terror will find a way.

Security specialists say this makes strong intelligence gathering the best defence, monitoring a list of people who might fall sway to the extremist call for violence.

"The big danger is someone not being on that list, perhaps having psychological issues, or being motivated by that ideology," said Dr Briskey.

"When those two elements join together, you get somewhere where there is unfortunately a real risk."