Knockd, to secure your ports on Linux

[ Thanks to linuxaria for this link.

“Installation: Knockd it’s available in the repository of the
major distributions, i’m using it on Ubuntu/Debian where the
package it’s available.

“Configuration: knockd reads all knock/event sets from a
configuration file. Each knock/event begins with a title marker, in
the form [name], where name is the name of the event that will
appear in the log. A special marker, [options], is used to define
global options.”

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