Hi,
I've been reading this forum and it seems that there's a lot of people here are having the same problem with high CPU usage with their computers. I think I may know what causes it - I don't know how to fix it but may be a staff member/Avast software developer can investigate. Here's my scenario:
I've been using Avast free antivirus version 18.8.2356 (build 18.8.4084.0 - release date 11/15/2018) ever since it first came out on my Windows 7 Home edition SP1 64-bit laptop with no other additional security software installed except the default Windows Defender, and I have it set on manual update for both the virus definitions and the program. I occasionally update the virus definitions manually whenever they're out of date and it's been working OK for 3 years until a couple of weeks/10 days ago when I manually update the virus definitions version 210825-8 (release date 8/25/2021 9:16:11 AM), and immediately (well, may be not immediately but a few minutes later since I didn't notice it right away until my laptop started to run slowly) AvastSvc.exe jumped at 25% CPU usage and keeps running that high ever since.
In short, since I didn't install any new software on my laptop for years and I've been using the same version of Avast also for years, therefore I think there must be something in the new virus definitions that cause it. I hope this sheds some light on the problem.
Please HELP,
Thank you.