Cybersecurity expert Mark Rasch says law enforcement is still working on how to treat domestic terrorism online.

Extremists are far too at home on social media. Whose job is it to root them out?

A former Facebook policy worker says platforms have a lot to lose if they don't crack down on misinformation.

“Large media corporations have a duty to take on this challenge,” one expert says.

And what can social media companies do to intervene?