Cisa did not identify who was behind the attack; which agencies and organisations had been breached; or what information had been stolen or exposed.

Meanwhile, US President-elect Joe Biden said he would make cyber-security a "top priority" of his administration.

"We need to disrupt and deter our adversaries from undertaking significant cyber-attacks in the first place," he said. "We will do that by, among other things, imposing substantial costs on those responsible for such malicious attacks, including in coordination with our allies and partners."

SOURCE:BBC