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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

Content Security Policy (CSP)
An HTTP security header that controls which resources a browser is allowed to load for a web page, preventing XSS and data injection.
Input Validation
The process of verifying that user-supplied data meets expected formats, types, and ranges before processing it.
Brute Force Attack
An attack method that systematically tries all possible combinations of passwords or keys until the correct one is found.
Rate Limiting
A technique that controls the number of requests a client can make to a server within a specified time period.
Security Headers
HTTP response headers that instruct browsers to enable security features like XSS protection, framing prevention, and content type enforcement.
Security Hardening
The process of reducing a system's attack surface by disabling unnecessary services, applying patches, and configuring security controls.
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