In a blog post Tuesday, Microsoft said it observed hackers attempting to “gain initial access to target organizations.” According to Microsoft, those involved included hacking groups called Linen Typhoon and Violet Typhoon—which Microsoft said are linked to the Chinese government—and China-based group Storm-2603.

Microsoft Corp. has determined that China-linked hacking groups are targeting deployments of its SharePoint file sharing platform. The company detailed its findings in a blog post published today.

Two Chinese nation-state actors and one China-based threat actor have tried to exploit the vulnerability for weeks, Microsoft said.