Security Beginner

What is Firewall Rules?

Configuration entries that define which network traffic is allowed or blocked based on source, destination, port, and protocol.

Firewall rules specify allow/deny decisions based on traffic attributes: source IP, destination IP, port number, protocol (TCP/UDP), and direction (inbound/outbound). Rules are processed in order — first match wins.

Best practices include default-deny (block everything, explicitly allow needed traffic), least privilege (minimal ports open), logging denied traffic, separating inbound/outbound rules, and regular rule review. Cloud security groups function as virtual firewalls with similar rule structures.

Learn More About This Topic

Firewall Configuration: The Complete Guide

Directly covers this topic

Linux Firewall Configuration

Related reading

Linux Security Auditing

Related reading

Related Terms

A one-way function that converts input data into a fixed-size string of characters, used for data integrity and password storage.

A regularly updated list of the ten most critical web application security risks, published by the Open Web Application Security Project.

SIEM (Security Information and Event Management)

A platform that collects, correlates, and analyzes security events from across an organization to detect threats and incidents.

SOC (Security Operations Center)

A centralized team and facility responsible for monitoring, detecting, analyzing, and responding to cybersecurity threats 24/7.

XSS (Cross-Site Scripting)

An attack that injects malicious scripts into web pages viewed by other users, potentially stealing data or session tokens.

JWT (JSON Web Token)

A compact, self-contained token format used for securely transmitting information between parties as a JSON object.

View All Security Terms →