The hackers behind the initial wave of attacks exploiting a zero-day in Microsoft SharePoint servers have so far primarily targeted government organizations, according to researchers and news reports.

The newly discovered flaw in Microsoft's SharePoint software has allowed hackers to target dozens of companies and organizations. Only a partial fix has been issued.

A sweeping cyber espionage operation targeting Microsoft server software compromised about 100 organizations as of the weekend, two of the organizations that helped uncover the campaign said.

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.

Microsoft has released a critical patch for a security flaw in its SharePoint software. Hackers actively exploited this vulnerability, targeting businesses and US government agencies. The company issued the fix between July 19 and 20.