The United States says a Chinese hacker group has breached email accounts of two dozen government agencies, including the State Department -- a move which Microsoft and the White House said was aimed at acquiring sensitive information.
Microsoft and US national security officials claimed on Wednesday that US government agencies were infiltrated by a Chinese hacker group, code-named Storm-0558 by Microsoft.
A State Department spokesperson told CNBC that the department "detected anomalous activity, took immediate steps to secure our systems and will continue to closely monitor and quickly respond to any further activity."
The Department of Commerce, which has sanctioned Chinese telecom firms, was also breached, the Washington Post first reported.
Microsoft also said late Tuesday that it had mitigated an attack by “a China-based threat actor” that primarily targets government agencies in Western Europe and focuses on espionage and data theft.
The hacking group also compromised personal accounts “associated” with the agencies, likely employees of the agencies.
“The Senate Intelligence Committee is closely monitoring what appears to be a significant cyber security breach by Chinese intelligence,” Senator Mark Warner said Wednesday.
He said that China "is steadily improving its cyber collection capabilities directed against the US and our allies."
"Close coordination between the US government and the private sector will be critical to countering this threat," said Warner, who is chair of the Select Committee on Intelligence.
Back in May, Microsoft claimed that a Chinese government-backed hacking group had managed to insert a computer code that blended into Microsoft Windows systems, and evaded detection while maintaining access and gathering information.
It said the group, dubbed 'Volt Typhoon', had carried out the hack.
The group, it said, targeted organizations from telecommunications to transportation hubs, Western intelligence agencies and Microsoft itself, as well as the crucial US military outpost of Guam in the Pacific Ocean.
According to the Washington Post, the State Department discovered the intrusion on June 16 and notified the company the same day.
And days later, Washington formally accused China of widespread destabilizing activities in cyberspace, including through a massive breach of Microsoft email systems.
China, for its part, has branded the US as the “biggest threat to global cybersecurity,” saying that Washington “knowingly abuses technology” for spying and a range of other purposes.