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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.

Related Terms

Data Loss Prevention (DLP)
A strategy and set of tools that detect and prevent unauthorized transmission of sensitive data outside an organization.
Man-in-the-Middle Attack
An attack where the attacker secretly intercepts and potentially alters communication between two parties who believe they are communicating directly.
Principle of Least Privilege
A security principle where users and programs receive only the minimum access rights needed to perform their specific tasks.
Vulnerability Scanning
Automated testing that identifies known security weaknesses in systems, applications, and network infrastructure.
DDoS (Distributed Denial of Service)
An attack that floods a target server or network with traffic from multiple sources to overwhelm it and deny service to legitimate users.
OWASP Top 10
A regularly updated list of the ten most critical web application security risks, published by the Open Web Application Security Project.
 View All Security Terms →