A series of cyberattacks targeting Microsoft collaboration software, specifically SharePoint, have been linked to Chinese hackers and threat actors.

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.

In ongoing hacks, Microsoft says it has identified two Chinese hacking groups taking advantage of a key software flaw.