Little Flocker is the only app I found, but it was apparently discontinued in 2017. Overall, it doesn’t look like this topic is popular. However, it seems as important as a network firewall to me.
Consider the following threat scenario: Pretty much any program that runs on my computer (from my user) can read almost any file without me knowing it. For example, it can read my Firefox profile folder, and steal any web session. Note that FF cookies are not encrypted on disk, and the network firewall may not prevent the leakage in cases when the malware pretends to have legitimate reasons to talk to the internet.
If you are aware of anything similar for other operating systems, please share as well.