On macOS, open Activity Monitor and click on the Network tab. While viewing network usage, look for unfamiliar processes or applications consistently sending or receiving data in the background.

You can start with Activity Monitor, which shows you what's running on your Mac. Here's how: Open Activity Monitor from Applications > Utilities.

How to monitor drive activity from Task Manager To check the drive activity through Task Manager, use these steps: Open Start. Search for Task Manager and click the top result to open the app.

There’s no easy way to log this data automatically though, so you’ll have to run Activity Monitor regularly and manually note down the figures you see, to check for performance issues over time.