While the government's efforts were great, they also underscored the difficulty in going after those behind cyberattacks.

The three countries have conducted sophisticated, large-scale hacking attacks across multiple U.S. industries.

The FBI has taken over the probe into a deadly plane crash near the Hartford-Brainard Airport in Connecticut after investigators determined it appeared to be deliberate, rather than the result of an accident.

Internet-connected and driverless cars could be targets for hackers so the auto industry must ensure vehicles have built-in cyber security protection, a top U.S. Justice Department official said.

Hacker based in Iran allegedly gained remote access to a computer controlling the Bowman Avenue Dams flood-control structure.

Hackers linked to the Iranian government launched cyber-attacks on some four dozen U.S. financial institutions and a flood-control dam above New York City in forays meant to undermine U.S. markets and national security.

A key figure is missing in the court documents outlining the biggest computer attack ever of the U.S. financial system: the actual hacker.

The U.S. Defense Department is sending personnel on tours with private cyber security companies and bringing in specialists from those companies to gain the skills necessary to defend military networks from hackers.