It's the second major network disruption on Ukrainian government sites in about a week.

"If they succeed this will probably be one of the most important cybersecurity improvements this decade," one security researcher said.

It's a rare public acknowledgement.

The spy agency GCHQ is using digital tools originally developed to tackle online propaganda and recruitment material from the Islamic State, sources told The Times of London.

The tech coalition rejected the GCHQ's suggestion that adding a law enforcement official to a group chat or call would not threaten civil liberties or security.

GCHQ head Jeremy Fleming revealed that the U.K. has conducted a proactive cyber campaign against ISIS, touting the notion of using offensive cyberattacks to counter violent extremism.