Since the last update avast slows down my computer extremely whenever i download anything from steam or anywhere else to the point that watching YouTube is impossible. Furthermore making exceptions doesn’t help and when I tell avadt to turn off for 10min it blocks the access to the internet! WTF?!
anytime I need to download a big file my pc is becoming absolutely useless! That can’t be, I need to be able to work while downloading files!
Hey, could I ask you to check the system tray and see if you have a process called “LocalServiceNoNetworkFirewall” with a sub-point called “BFE”?
I’ve had an issue which sounds the same. It has a high usage of “Disk” and some CPU usage. It appeared to block internet access to the point where it took extremely long, just to go to the simplest sites. Also, when it really acted up, it made my computer lag like crazy. Just opening Start was a serious challange.
I’ve just uninstalled my Premium Avast and it seemed to have solved the issue completely.
LocalServiceNoNetworkFirewall appears to be a Microsoft program, which has ties to Windows Defender. So I suspect that Avast and Windows Defender are having relationship issues at the moment.
In any case, does any of what I just said sound familiar? Are you able to find the “LocalServiceNoNetworkFirewall” process, or do I need to start up a new thread? 
UPDATE: I’ve re-installed Avast Premium and everything works fine now. So a simple, complete, re-installation fixed my issue, apparently.
Thanks for the feedback.
Free Avast Version 20.5.2415 (20.5.5410.561)
Windows 7 Pro 64bit
only other related program installed is Avadt Cleanup Premium and Avast is the only AV i use since winXP
Reinstalling unfortunately didn’t solve the problem. I also can’t see any heavy usage of CPU, Disk or Network (Downloading 100GB usually takes not longer than 30min, no web it takes almost 2 hours)
It just makes absolutely no sense… nothing is ever at 100% usage but still working with heavy programs and streaming becomes all over sudden impossible. Didn’t had that problem a few months ago… exactly same system
Did you try a clean reinstall…?
yes did that already 
I’m having the same apparent issue. The fix recommended by most Windows 10 users is to change the Firewall settings to “default settings”. But that is greyed out with a notice that Avast Premium Security is in charge of the settings. This loss of internet connectivity for a few minutes every few minutes is getting really tiresome. Does anyone have a fix? Has Avast released a newer version of Premium Security that addresses this?
You could try the latest beta: https://forum.avast.com/index.php?board=15