I have a 5GB a month data contract with Spusu, which is not great. I tether from my smartphone to my laptop running latest Debian Linux.
I also use an image and movie blocker on Firefox, to keep the bandwidth at bay, on top of ad blockers.
This morning I spent about an hour doing some Google searches, all landing to text only sites. No pictures, no videos, no ads were loaded. I checked on the network page and I had consumed 450MB of data in an hours, which is next to impossible.
My system is updated and security patched. The data comes from the tethering. All other apps on my phone have negligible traffic.
I have checked "netstat -l" and it doesn't appear to show any programs listening.
I am at loss here, unless Google steals data in the background? But I also have an "AI result" blocker.
???