olemus
portide valikuline avamine ja sulgemine
vastavalt nende pääsupoliitikale

yourdictionary.com:
allowing or blocking network packets into or out of a device or the network based on their application (port number)

ülevaateid
https://www.senki.org/exploitable-port-filtering/

vt ka_
- pakettide filtreerimine
- portide skaneerimine