fwknop: fwknop (Single Packet Authorization and Port Knocking) fwknop: fwknop: fwknop stands for the "FireWall KNock OPerator", and implements an fwknop: authorization scheme called Single Packet Authorization (SPA). fwknop: This method of authorization is based around a default-drop packet fwknop: filter and libpcap. fwknop: fwknop: fwknop: fwknop: fwknop: