Truck runs over 84 French people

[abaris]

Exactly: no amount of surveillance will prevent all attacks. People get upset at the amount of surveillance and attacks 'slip through the net' anyway. People are more likely to die on the roads (in a car accident) than in a terrorist attack but somehow we must suspend our freedoms and let the terrorists terrorize us.

Some security measures are necessary. Such as keeping it tight on airports and before boarding a plane.

Some security measures simply don't work. Such as indiscriminate data collection, since the services are drowning in information which they can't process anymore.

And some attacks, such as this one - driving a truck into soft targets - will never be prevented. They couldn't very well cage in the whole Cornige.