Isn't Little Snitch essentially an interactive firewall? Rather than silently denying/allowing traffic, it needs the user's decision until a connection is white/black listed? Why would this not be allowed on Linux? (other than the app doesn't exist, yet)
However, if you allow everything to 80/443, the extensions would still be able to connect to their servers. Maybe the browsers should add the ability to allow/deny connections per extension.
