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iptables is a user-space utility program that allows a system administrator to configure the IP packet filter rules of the Linux kernel firewall, implemented as different Netfilter modules. The filters are organized in a set of tables, which contain chains of rules for how to treat network traffic packets.
IPFire is a hardened [3] open source Linux distribution that primarily performs as a router and a firewall; a standalone firewall system with a web-based management console for configuration. IPFire originally started as a fork of IPCop [ 4 ] and has been rewritten on basis of Linux From Scratch since version 2. [ 5 ]
Uncomplicated Firewall (UFW) is a program for managing a netfilter firewall designed to be easy to use. It uses a command-line interface consisting of a small number of simple commands, and uses iptables for configuration.
Netfilter is a framework provided by the Linux kernel that allows various networking-related operations to be implemented in the form of customized handlers.Netfilter offers various functions and operations for packet filtering, network address translation, and port translation, which provide the functionality required for directing packets through a network and prohibiting packets from ...
For publicly accessible services such as web and mail servers the port number is important. For example, port 443 connects through a socket to the web server software and port 465 to a mail server's SMTP daemon. [8] The IP address of a public server is also important, similar in global uniqueness to a postal address or telephone number.
It provides firewall features by acting as a front-end for the Linux kernel's netfilter framework. firewalld's current default backend is nftables. Prior to v0.6.0, iptables was the default backend. [3] Through its abstractions, firewalld acts as an alternative to nft and iptables command line programs.
The iptables-translate tool can be used to translate many existing iptables rules to equivalent nftables rules. [ 4 ] [ 5 ] Debian 10 (Buster) , among other Linux distributions , uses nftables along with iptables-translate as the default packet filtering backend.
A server can determine that a given mail message is spam, e.g. because it was addressed to a spam trap, or after trusted users' reports. The server may decide that the IP address responsible for submitting the message deserves tarpitting. Cross-checking against available DNSBLs can help to avoid including innocent forwarders in the tarpit database.