I have run into an issue where Avast’s File Shield will drain almost all of my cpu power when it tries to scan large .exe files like app installers or a user-created self-extracting 7z SFX (.exe) archives. I first encountered the problem whenever I created a large (>100MB approx) 7z SFX file where, once 7zip was finished creating the file, File Shield would use all remaining CPU time to scan them, leaving just enough CPU for the rest of the system to keep running. This also happens when opening/running, copying/moving, deleting, or even just right-clicking the file in Explorer. Only files/archives with the .exe extension seem to be affected (.zip, .rar, .7z, .iso, etc. are fine).
When File Shield does this it also renders the Explorer window the file was opened from completely frozen. And by “frozen” I don’t mean “not responding” by Windows’ standards, I mean it completely freezes and does nothing at all. The process in Task Manager doesn’t say “not responding” next to it and no “stopped responding” dialogue will appear no matter how many times I click in the Explorer window. If I try to restart Explorer.exe the offending window will refuse to close and an “end process” dialogue will appear but it will do nothing, forcing me to reboot.
I discovered that it wasn’t just 7z SFX .exe files affected after I downloaded an installer for “Portal Prelude” (a top-rated mod for the much-loved Valve PC game “Portal”). When I opened my Downlads folder after the download, Avast File Shield decided to use >90% of my CPU (yes, it was AvastSvc.exe alone using this much, not the total system usage) leaving next to nothing for the rest of my system to run on. Infact it left so little that I had to force-shutdown my PC, risking data loss, because there wasn’t even enough processing power left for the services required to open the Start menu, let alone open the Avast GUI to get into the settings and temporarily disable the shields. After I rebooted I let my system settle down, disconnected from WiFi and temporarily disabled File Shield, removed all other files from my Downloads folder (including .zip files much larger than the “offending” .exe file), re-enabled File Shield, then ran a targeted scan on my Downloads folder to see exactly how long it would take to scan the file manually. The targeted scan completed successfully in just a few minutes with “normal” CPU usage (<30%), where as File Shield’s scan will use as much CPU as it can get but still take so long that I have to reboot just to abort it.
I’m aware that heavily compressed files require a lot of CPU power to decompress, scan and recompress. But using so much that it totally drains all of my CPU leaving nothing for vital system services and therefore rendering my system completely unusable is just taking the pee and needs to be fixed.
I have already tried repair and clean installations of Avast but these made no difference.
I am running Windows 10 Home from an SSD with an i5 processor (albeit, a legacy i5) and 12GB of RAM so my system is more than capable of handling files with high compression ratios, yet Avast File Shield is still able to more or less kill my CPU when scanning .exe files, especially large ones like app installers and large 7z SFX archives. The age of my processor shouldn’t make any difference. I can normally run CPU-intensive apps like FL Studio no problem.
Please fix this.