3 application-level firewalls for Linux distributions

“A packet filtering firewall, designed to regulate incoming and
outgoing packets from a network or an operating system, is akin to
security personnel guarding the entrance to a commercial or
residential property. Such a system has very little authority,
unless given additional powers, in what applications inside the
operating system or network are able to do.

That is where an application “firewall” comes into play. It is
designed to ensure that applications in an operating system (or in
some instances, a network) adhere to access control rules that
govern their “activities.” It should be noted that an application
firewall, like a stateful packet filter, is not a one-shot security
solution. It merely adds an extra layer of security to a system,
complementing other security protocols and systems in place.

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