A robust firewall.
Ranked in these QuestionsQuestion Ranking
Pro Comparatively easy to use
Easier to use than traditional firewall software, but more powerful due to design and workflow.
Pro Protects your privacy
Protects your privacy and helps to prevent unwanted connections.
Pro Protected even at login screen
Little Snitch rules work even at login screen. Even when receiving attempted connection alerts, once logged in LS has stopped and requested permission for them.