valentin,
when your antivirus doesnt have the signature, you will get INFECTED when you execute the program of your choice outside of a sandbox (because of compatibillity for example).
no matter if you have lines of direct "default deny" before that. YOU want to execute it.
in this scenario, the antivirus is your ONLY line of defense.
thats why the antivirus should be taken SERIOUSLY because it COULD protect you then.