President Donald Trump's top cyber and homeland security advisor said Monday that no US government systems had been hit by the world's biggest ransomware attack.

"As of today, no federal systems are affected," said Tom Bossert, adding that his hard-hit British counterparts now had a "feeling of control" over the sprawling attack, which affected computers in dozens of countries.

Bossert added that the "less than $70,000" of ransom money paid to release data locked by the virus appears not to have "led to any data recovery."