The standard Linux firewall used to define, manage, and inspect tables of IP packet filtering rules within the Linux kernel.

Note: In modern distributions, iptables may be replaced by nftables, but it remains a widely used and supported solution.

ALT Linux Wiki:
Firewall configuration using iptables -
https://www.altlinux.org/Iptables

Home page:
https://www.netfilter.org/projects/iptables/