CNN Business  — 

The White House on Sunday urged companies who believe their systems were compromised in the ransomware attack that targeted software vendor Kaseya to immediately report it to the Internet Crime Complaint Center.

“Since Friday, the United States Government has been working across the interagency to assess the Kaseya ransomware incident and assist in the response,” said Anne Neuberger, deputy national security advisor for cyber and emerging technology. “The Federal Bureau of Investigation (FBI) and the Cybersecurity and Infrastructure Security Agency (CISA) have been working with Kaseya and coordinating to conduct outreach to impacted victims.”

REvil malware hit a wide range of IT management companies and compromised hundreds of their corporate clients late last week. The cybercriminal gang, which is believed to operate out of Eastern Europe or Russia, targeted a key software vendor known as Kaseya, whose products are widely used by IT management companies, cybersecurity experts said.

On Saturday, President Joe Biden said that the US government is not certain who is behind the attack, but he has directed federal agencies to assist in the response.

“The fact is that I directed the intelligence community to give me a deep dive on what’s happened and I’ll know better tomorrow. And if it is either with the knowledge of and/or the consequence of Russia, then I told Putin we will respond,” Biden said Saturday, referring to his meeting with the Russian leader last month.

“We’re not certain. The initial thinking it was not the Russian government but we’re not sure yet,” he added.

- Brian Fung contributed to this report