Security 13-5How filter sets workA filter set acts like a team of customs inspectors. Each filter is an inspector through which incoming andoutgoing packages must pass. The inspectors work as a team, but each inspects every package individually.Each inspector has a specific task. One inspector’s task may be to examine the destination address of alloutgoing packages. That inspector looks for a certain destination—which could be as specific as a streetaddress or as broad as an entire country—and checks each package’s destination address to see if it matchesthat destination.A filter inspects data packets like a customs inspector scrutinizing packages.Filter priorityContinuing the customs inspectors analogy, imagine the inspectors lined up to examine a package. If thepackage matches the first inspector’s criteria, the package is either rejected or passed on to its destination,depending on the first inspector’s particular orders. In this case, the package is never seen by the remaininginspectors.INSPECTORFROM:TO:FROM:TO:FROM:TO:APPROVED
