Some Windows 10 features, such as Cortana and Bing search, continue sending data to Microsoft, even when they are turned off.
New analysis by Ars Technica showed that some apps and services will communicate with the software giant's servers, even when the user tells them not to by the software's various privacy settings.
In one example, a Windows 10 machine would periodically send data, said to be used for OneDrive, the company's cloud service, for reasons unknown -- even on a local account that isn't connected to a Microsoft account.
"It's not clear why any data is being sent at all," wrote Ars Technica editor Peter Bright in a blog post Thursday.
It's the latest in a long line of issues relating to Windows 10, released last month, which lands with a bevy of new internet-connected features. But some have accused Microsoft of trading-off user privacy in the process. Others have argued that some users are overreacting.
But in at least one case, information that can identify the user is also sent.
Cortana, the operating system's voice activated assistant, will send some data to Microsoft, even if the service is disabled. But that data contains an identifying computer ID that "persists across reboots," allowing Microsoft to determine all the Cortana requests from the same computer.
By analyzing internet traffic from one of his Windows 10 machines, Bright was able to show that some services would connect to Microsoft's servers through unencrypted channels, potentially opening up users to download traffic being intercepted.
"Disabling these services for those who don't want to use them should really disable them," said Bright. "And it's not at all clear that Windows 10 is doing that right now."
Other data was "impenetrable," preventing users -- and presumably malicious actors -- from seeing what data is sent to the company.
In a statement to the tech site, Microsoft said "no query or search usage data is sent" to the company, but did not elaborate much further. (We also reached out to Microsoft for comment, but did not hear back immediately.)