They found one of the terrorists phones dumped in a garbage can outside the theatre they attacked, and got the address of their hideout from the messages, so used just regular police work.
All these guys were already on watch lists for fighting in Syria and returning just nobody seems to ever watch the watch list.
You'd still have a telephone number. From that telephone number you could go to a judge and request a warrant for the telephone records. From there you could look at all the numbers dialed and received. Now you get a warrant for the addresses of the subscribers.
No bulk surveillance required, just honest police work within the confines of a valid and acceptable legal framework.
But then, if they'd used a CB radio, there'd have been no records on the device at all. You can go both lower and higher tech to avoid leaving a trail.
The fundamental issue our society faces is that the world people thought existed, pre-Snowden, wasn't all that bad. There are controls, a system of laws and warrants, judges have to approve requests for data, and companies hand it out only in cases where it's really justified. Terrorist used WhatsApp to send a message to his buddy before blowing up a football stadium? It is - literally - warranted.
Post Snowden we know that world didn't really exist, it was more a sort of theatre governments put on when they didn't care much about the outcome. So now the data is disappearing so nobody has it. It's not obvious that this is an improvement over restoring the world that was previously thought to exist, but that was apparently too unstable to survive.
That's roughly equivalent to 'if those documents had not been properly shred that data would not have been available'.
Each and every operation of this magnitude leaves a trail. The party perpetrating it will try what they can to erase that trail but that will always be an imperfect process.
Maybe next time the phone will be secured, they will scrub themselves of parking tickets, they will burn up their escape vehicle after a few minutes ride and so on. All the media has succeeded in doing is educate the terrorists about how to be more successful in evading capture and possibly being more successful in carrying out the attack in the first place.
France has something like 11,500 on the extremist watchlist. I'm not sure its practical to watch and monitor that many people with the staffing levels of French Intelligence without acting like the stasi
That's precisely the point being discussed. The "collect it all!" mentality of the intelligence agencies just increases the size of the haystack and does not actually result in stopping these incidents, as they are now spread too thin.
> does not actually result in stopping these incidents
My point was that collecting it all isn't necessarily about stopping incidents, it's about instantly knowing everything about a terrorist once they are identified through other means. There's certainly value there and the debate is whether or not the cost is too high.
My point was that the collect it all mentality is driven by the number of extremists on the list. It takes something like 20 agents to follow someone around the clock.
That means the DGSI would need 230,000 staff to follow all of the extremists all of the time
All these guys were already on watch lists for fighting in Syria and returning just nobody seems to ever watch the watch list.