The US military has drastically stepped up its secret hacking of foreign computer networks under the Trump administration, in a new effort to keep China, Russia, Iran and other adversaries on their heels, current and former US officials told NBC News on Sunday.

According to the officials, empowered with new legal authority from both Congress and President Donald Trump, the military's elite cyber force has conducted more operations in the first two years of the Trump administration than it did in eight years under Obama.