http://www.pbs.org/wgbh/frontline/fi...ror-in-europe/

FRONTLINE and ProPublica go inside Europe’s fight against terrorism — the missed warnings and the lingering vulnerabilities.
And the associated article:

https://www.propublica.org/article/h...n-to-terrorism

How Europe Left Itself Open to Terrorism

The ISIS attacks on France and Belgium exposed weaknesses in Europe’s approach to borders and information sharing that counterterror officials had warned about for years. The vulnerabilities remain largely unaddressed.
In interviews, some on camera with Frontline, counterterror veterans in Europe and the United States outlined systemic problems they said they had warned political leaders about for years. (ProPublica granted some anonymity because they are not authorized to speak publicly or because of security concerns.) The list includes:

•Weak and uncoordinated enforcement of Europe’s international borders, a situation aggravated by the chaotic influx of refugees from Syria.

•Differences in laws and security cultures that hamper intelligence-sharing and law enforcement cooperation among nations.

•Fragmented and incomplete databases, and the lack of a universal database of terror suspects effectively used and supplied by all European nations.

•Short prison sentences for terrorism and violent crime that have freed ex-convicts to play prominent roles in the jihad.

•Limited resources and support for security forces in some nations, such as Belgium and Greece — a weakness that terrorists have studied and exploited.