I am seeing something similar - and I have been running Brave for about 6 months now. Here is what I found:
Last night I received an email from Comcast telling me I had used 75% of my 1.2TB data limit.
This morning, less than 12 hours later - 90%
This afternoon - 100%.
Before I called Comcast to yell about there being no way I have used that much, I did a little digging. Using NetHogs, I am seeing that Brave is consistently receiving about 5MB/sec. I closed everything down, rebooted my computer, and started a fresh Brave instance - immediately it jumped to the same usage - before I even went to a web page. (The first line is my VPN - which is why it is a bit larger than the Brave process)
2004 $ ps -eaf |grep 20108
merung 20108 20078 13 14:59 ? 00:00:02 /opt/brave.com/brave/brave --type
=utility --field-trial-handle=5207069642631551181,8307081892597075190,131072 --en
ookmarks,UnifiedConsent,WebXR,WebXrGamepadModule --lang=en-US --service-sandbox-t
ype=network --disable-webrtc-apm-in-audio-service --service-request-channel-token