Thousands of Australian businesses and government agencies are scrambling to patch a series of major vulnerabilities in more than 7000 Microsoft Exchange servers across the country after a global attack from a China-based state-sponsored hacking group.

Last week Microsoft quickly sent out patches for four zero-day exploits, allegedly used by China-based hacking group HAFNIUM. A zero-day exploit is a vulnerability that was previously unknown to the software vendor. “Zero-day” refers to the fact that the developers have “zero days” to fix the newly exposed problem, which might already have been exploited by hackers.