Automatically restore firewall filter rules
Every administrator has to determine how to protect a network reliably against unauthorized access and ensure that the (sub)network fulfills its task as expected and is not misused as a starting point for malicious activities. At the network level, you have various ways and means at your disposal, including, for example, managing credentials for authenticating users (e.g., via PAM and LDAP), the appropriate selection of correctly configured services, and correct network device configurations.
Routers and firewalls are often used to isolate individual network segments, and the Linux kernel manages the firewall rules in the system's RAM. I demonstrate different methods for permanently storing your firewall settings by using iptables, thus removing the need to enter them again whenever you reboot.
Firewall Protection
From a network perspective, a firewall's primary objective is selecting and limiting the network packets that reach a network via a monitored interface on another network. In practice, firewalls are deployed not only as software directly on the system to be protected, but also in the form of separate hardware appliances that often combine various services under one roof.
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