Microsoft issued an emergency fix to close off a vulnerability in its SharePoint software that hackers have exploited to carry out widespread attacks on businesses and at least some federal agencies.

Researchers say Chinese actors, along with other criminal hackers, exploited a security flaw in SharePoint software widely used by governments and businesses.

US government agencies and private businesses are facing a significant cyber threat following an unprecedented global attack on Microsoft servers. Authorities are investigating after thousands of SharePoint servers were compromised recently,

Microsoft said the company has been "coordinating closely with CISA, DOD Cyber Defense Command, and key cybersecurity partners around the world throughout our response."

A global attack on Microsoft server software used by thousands of government agencies and businesses to share documents within organisations is likely the work of a single actor, a cybersecurity researcher said on Monday.

Microsoft released an emergency security patch on Sunday to “mitigate active attacks targeting on-premises servers.”

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Britain's National Cyber Security Centre (NCSC) said on Monday it had detected a "limited number" of UK-based victims in an ongoing hacking campaign that has affected servers using Microsoft's SharePoint system.