President-elect Joe Biden said he intends to make cybersecurity “a top priority” amid reports of a widespread cyberattack across U.S. government agencies and private companies led by suspected Russian hackers.

Biden’s pledge came as President Donald Trump has been silent on the hack, which exploited widely used Orion software from SolarWinds Corp.

“There’s a lot we don’t yet know, but what we do know is a matter of great concern,” Biden said in a statement.

“I want to be clear: My administration will make cybersecurity a top priority at every level of government -- and we will make dealing with this breach a top priority from the moment we take office,” he said.

The Cybersecurity and Infrastructure Security Agency earlier Thursday said the hack posed a “grave risk” to federal, state and local governments in addition to critical infrastructure and the private sector. The agency said the hackers demonstrated “sophistication and complex tradecraft” and ousting them from compromised networks will be “highly complex and challenging.”

The attackers got into computer networks by installing a vulnerability in Orion software from SolarWinds Corp., which is widely used by government agencies and the private sector.

CISA said it has evidence that the hackers also used other methods to infiltrate networks, in addition to Orion software. Those remain under investigation.

— With assistance by William Turton