Accidently blocked an app. in Comodo firewall

If I accidently block an application or terminate a connection in Comodo firewall, is there anyway to unblock it? After installing comodo and using it's default settings, will it automatically block and deny all bad instrusions or do custom rules have to be made?

 

If you accidentally block an application you can remove or change the rule in D+ or the Firewall by clicking either on the main GUI, advanced, security policy.

While CFP has predetermined rules for browsers, mail clients etc you'll set custom rules for your other apps. Once installed, at your leisure, open each program and carefully select each pop up. After a couple days, unless installing new programs, you'll hardly even notice it's there.

Read the help section, all of it.