Hello,
thanks for reporting this. Here is our current understanding of the problem (that only occurs on MacOS 10.15 Catalina):
we think that Apple has a bug in it’s filesystem code (probably something with Apple Filing Protocol, Apple’s network drive protocol, used for sharing files and doing time machine backups over local network, as most of the people affected have such drives). It seems that Avast File Shield being active dramatically increases the chance of the issue manifesting for a handful of users (we have a case where it seems the same issue has occurred without Avast even being installed…). The bug causes certain filesystem-related operations to freeze indefinitely; programs which freeze like this are not killable. Since when Safari or Apple Mail app open a page/email, they spawns a helper process which during it’s initialisation always freezes if the issue occurs; this is why the issue most often manifests as a browser problem; however other processes may freeze instead when trying to do similar operations as the helper process does during start, which can lead to various other issues and freezes. We had several people cooperate with us, but eventually the issue stopped occurring for them; even when using the Apple file sharing and backups on several test machines we are not able to reproduce the problem locally.
Please ensure that you are running the latest Catalina version.
Currently the only way how to work around this seems to be disabling Avast File Shield or uninstalling Avast.
What can be done: Apple engineers have asked us to provide them a diagnostic package from their sysdiagnose tool. Please if you can, keep a Terminal app running, and when the issue occurs, run command
sudo sysdiagnose
in the terminal. This will require some interaction, output should be a file /var/tmp/sysdiagnose_some_other_stuff.tar.gz . I am however afraid that it is likely that the command will freeze. We were told that in that case it may be worth it to run this command immediately after the computer is restarted instead. Please send this file to ondrej.kolacek <at> avast.com together with info if it has been generated during the freeze or after the restart; we will analyse it and forward it to the Apple personnel.
We are currently rewriting Avast File Shield to use the new Apple’s Endpoint Security framework in a hope that this will stop us triggering the issue; however this will take a while yet.
We apologise for the issue and it's impact. We are doing all we can to solve the issue.
Kind Regards,
Ondrej Kolacek