Linux: how to work with the network, firewall, and security?

Ensuring network security and proper firewall management in Linux represent a fundamental stage of preparing any server for operation in a public network. At the same time, it is important to remember a simple rule: timely installation of security updates and regular backups always have a higher priority than the most complex and delicate firewall configuration. Set up automated backups of critical data to remote storage and be sure to implement two-factor authentication for all user accounts with administrator privileges.

To filter incoming and outgoing network traffic in modern Linux distributions, the UFW utility is used as a simple interface for managing filtering tables, or the more powerful nftables tool. The basic security principle consists of blocking all incoming connections by default, followed by allowing only those ports that are necessary for the functioning of your services. For example, if the server operates exclusively as a web node, you must open only the standard ports for HTTP and HTTPS traffic, as well as the SSH remote access port.

Monitoring network connections and checking open ports are performed using classic diagnostic utilities such as ss or netstat. An administrator must regularly check which processes are listening on network interfaces to promptly detect unauthorized launching of extraneous network services. It is also recommended to use network intrusion prevention tools that analyze logs for suspicious activity and automatically block attackers' IP addresses.

A comprehensive approach to network security also includes the proper configuration of kernel parameters via the sysctl.conf file, which protects the server from common network attacks such as SYN flood or IP spoofing. Regular auditing of open ports, updating the package base, and strict control of access rights create a reliable defense line that minimizes the likelihood of infrastructure compromise through network vulnerabilities.