PARIS -- French police on Monday identified another of the ISIS terrorists who attacked in Paris last month. Seven have not been named. Three are still unidentified.

Foued Aggad, a 23-year-old French citizen, left in 2013 to join ISIS in Syria. But then somehow he slipped back into France -- and helped to gun down 90 music fans at a the Bataclan Concert Hall, before being killed at the scene.

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Police had no idea who he was, until Aggad's mother got a text message from Syria saying her son had been killed on November 13, the day of the attacks. That let forensics teams to match DNA from the body found in the Bataclan to samples provided by the Aggad family.

Only one of the core group of Paris attackers is still alive. Salah Abdeslam escaped --and is presumed to be on the way -- or even already in -- Syria.

Salah Abdeslam. CBS News

Also still alive and on the wanted list, are all those who provided support, says anti-terrorism consultant Jean Charles Brisard,

"Probably more than 20 individuals involved in one way or another to provide logistics, support, transportation, financing for this network," he said.

One such suspect is Mohammed Abrini -- seen on surveillance video in one of the terrorists' cars two days before the attacks.

With more than 2,000 property searches in less than a month, and more than 250 arrests, the pressure is on anyone in France who has been to Syria or has links to extremists. But there are more than 10,000 of them.

"We need around 20 to 30 agents to follow 24 hours a day on a single individual," said Brisard.

ISIS has lost a lot of ground on the battlefield so it's relying on video of the Paris attacks to promote its image as a winning cause, to entice what it relies on -- a steady stream of new foreign recruits.