While Trump has said little about the hacking of numerous US agencies, President-elect Biden signals that his administration will seek accountability for the breaches.

President-elect Joe Biden on Tuesday assailed the Trump administration for failing to fortify the nation’s cyber defenses, and called on President Donald Trump to publicly identify the perpetrator of a massive breach of U.S. government agencies — a hack some of Trump’s top allies have blamed on Russia.

Biden, who is being briefed on high-level intelligence in preparation for taking office next month, said planning for the hack began as early as 2019. Several federal agencies, including the Treasury Department and the Department of Energy, have said they were targeted.

“There’s still so much we don’t know,” Biden said during a news conference in Wilmington, Delaware. “But we know this much: This attack constitutes a grave risk to our national security. It was carefully planned and carefully orchestrated.”

The U.S. government has not made a formal assessment of who was behind the attack, but both Secretary of State Mike Pompeo and Attorney General William Barr have said all signs point to Russia. But Trump, who has long sidestepped blaming Moscow for its provocations, has not followed suit and has instead suggested — without evidence — that China may have carried out the hack.

The breach of the Treasury Department began in July, but experts believe the overall hacking operation began months earlier when malicious code was slipped into updates to popular software that monitors computer networks of businesses and governments.

“The truth is, the Trump administration failed to prioritize cybersecurity,” Biden said. “This assault happened on Donald Trump’s watch, while he wasn’t watching.”

Given Trump’s reluctance to publicly blame Russia, it appears likely that any formal U.S. retaliation for the hacking will fall to Biden. The president-elect said he would work with allies to set up international rules to hold nation states accountable for cyberattacks and vowed that his administration would make cybersecurity a top priority.