Weekend attacks compromised about 100 organisations
May hacker contest uncovered SharePoint weak spot
Initial Microsoft patch did not fully fix flaw

LONDON, July 22 (Reuters) - A security patch Microsoft (MSFT.O), opens new tab released this month failed to fully fix a critical flaw in the U.S. tech giant's SharePoint server software, opening the door to a sweeping global cyber espionage effort, a timeline reviewed by Reuters shows.
On Tuesday, a Microsoft spokesperson confirmed that its initial solution to the flaw, identified at a hacker competition in May, did not work, but added that it released further patches that resolved the issue.
It remains unclear who is behind the spy effort, which targeted about 100 organisations over the weekend, and is expected to spread as other hackers join the fray.
In a blog post Microsoft said two allegedly Chinese hacking groups, dubbed "Linen Typhoon" and "Violet Typhoon," were exploiting the weaknesses, along with a third, also based in China.
Microsoft and Alphabet's (GOOGL.O), opens new tab Google have said China-linked hackers were probably behind the first wave of hacks.
Chinese government-linked operatives are regularly implicated in cyberattacks, but Beijing routinely denies such hacking operations.
In an emailed statement, its embassy in Washington said China opposed all forms of cyberattacks, and "smearing others without solid evidence."

The vulnerability opening the way for the attack was first identified in May at a Berlin hacking competition, opens new tab organised by cybersecurity firm Trend Micro (4704.T), opens new tab that offered cash bounties for finding computer bugs in popular software.
It offered a $100,000 prize for so-called "zero-day" exploits that leverage previously undisclosed digital weaknesses that could be used against SharePoint, Microsoft's flagship document management and collaboration platform.
The U.S. National Nuclear Security Administration, charged with maintaining and designing the nation's cache of nuclear weapons, was among the agencies breached, Bloomberg News said on Tuesday, citing a person with knowledge of the matter.