It was originally thought to be an issue for Sierra and El Capitan OSs but there’s reports for others as well. One symptom is high CPU usage (possibly trustd and MRT) as shown in Activity Monitor app. The machine becomes sluggish and system logs get accordingly filled.
If affected, see the article comment section here which includes workarounds:
eclecticlight.co/2020/10/19/app … nd-mrt-17/
[MRTsecurity-configuration updates are one of the so called background (silent) ones: