The White House is concerned over a hack of Microsofts Exchange email software that the tech company believes originated in China.


The U.S. government has expressed deep concern over an attack on Microsoft’s Exchange email software that the tech giant believes came from China.


Microsoft executive Tom Burt revealed the breach in a blog post on Tuesday and announced the company would address security flaws he said had allowed hackers to gain access to Microsoft Exchange servers.


The Microsoft Threat Intelligence Center (MSTIC) is highly confident that the attacks were carried out by a “state-sponsored threat actor” based in China which they named Hafnium.


The tech company said Hafnium had tried to steal information from groups such as infectious disease researchers, law firms, higher education institutions, and defense contractors.


“This is an active threat,” White House press secretary Jen Psaki said on Friday. “Everyone running these servers—government, private sector, academia—needs to act now to patch them.”


On Saturday, the US National Security Council said it was “essential that any organization with a vulnerable server take immediate measures” to determine if they had been targeted.


A spokesman for the Chinese government told Reuters news agency that the country was not behind the hack. Beijing has repeatedly rejected U.S. accusations of cyber-crime.


More than 20,000 organizations have been compromised in the U.S. with many more affected worldwide as a result of cyberattacks, Reuters reported.