A widespread cyberattack targeting Microsoft’s (MSFT.O) server software used by thousands of government agencies and businesses for internal document sharing was likely orchestrated by a single actor, a cybersecurity researcher said on Monday.
Microsoft issued an alert on Saturday warning of “active attacks” on on-premise SharePoint servers.
The company clarified that SharePoint Online, part of the Microsoft 365 cloud suite, was not affected by the exploit, which is considered a “zero-day” vulnerability due to its previously undiscovered nature.
“Based on the consistency of the tradecraft seen across observed attacks, the campaign launched on Friday appears to be a single actor. However, it’s possible that this will quickly change,” Rafe Pilling, director of Threat Intelligence at Sophos, a British cybersecurity firm.
That tradecraft included the sending of the same digital payload to multiple targets, Pilling added.
Microsoft said it had “provided security updates and encourages customers to install them,” a company spokesperson said in an emailed statement.
It was not clear who was behind the ongoing hack. The FBI said on Sunday it was aware of the attacks and was working closely with its federal and private-sector partners, but offered no other details.
Britain’s National Cyber Security Centre did not immediately respond to a request for comment.
The Washington Post said unidentified actors in the past few days had exploited a flaw to launch an attack that targeted U.S. and international agencies and businesses.
According to data from Shodan, a search engine that helps to identify internet-linked equipment, over 8,000 servers online could theoretically have already been compromised by hackers.
Those servers include major industrial firms, banks, auditors, healthcare companies, and several U.S. state-level and international government entities.
“The SharePoint incident appears to have created a broad level of compromise across a range of servers globally,” said Daniel Card of British cybersecurity consultancy, PwnDefend.
“Taking an assumed breach approach is wise, and it’s also important to understand that just applying the patch isn’t all that is required here.”
