Extremists' use of technology is a persistent threat, experts warn.
U.S. and European governments have been pressuring social media companies including Twitter, Facebook Inc and Alphabet Inc's Google to fight harder against online radicalization.
Twitter has closed down 125,000 accounts promoting extremism since last year.
We need to target potential terrorists with the techniques of our digital ad companies, who know you better than your mother does.
Experts warn that a cyber attack on the national grid or water infrastructure could have "catastrophic" effects.