Sen. Richard Blumenthal (D., Conn.) told MSNBC host Andrea Mitchell on Thursday that the Obama administration should have responded more aggressively to North Korea in November 2014 after the country reportedly waged a cyber attack against Sony Pictures Entertainment.

Mitchell asked Blumenthal how concerned he was about North Korea's cyber capabilities as another weapon of choice that could be used against the United States.

"Very deeply concerned and that is a great question, Andrea, that very often is ignored," Blumenthal said. "The cyber capabilities of the North Koreans and many of our adversaries are well beyond what the public understands."

He went on to say that some military leaders who have briefed the Senate Armed Services Committee have said the greatest threat from North Korea is cyber, and that the U.S. government needs to ensure building cyber defenses is a priority.

"Sen. [John] McCain (R., Ariz.), the chairman of the Armed Services Committee, and I have repeatedly raised with officials of this administration and of past administrations the lack of clear policies to define what is an act of war that will prompt the kind of response that we need to do," Blumenthal said.

He emphasized this point by pointing to the North Korean attack on Sony and how the Obama administration was not aggressive enough.

"The attack on Sony by North Koreans reportedly perhaps should have prompted a more aggressive response by the Obama administration if there were a defined policy about what constitutes an act of war," Blumenthal said.

Trump delivered a strong warning Tuesday against North Korea if the rogue country makes any future threats against the United States.

"North Korea best not make any more threats to the United States," Trump said. "They will be met with fire and fury like the world has never seen."