What is a Firewall?
A firewall is a network security system that monitors and controls incoming and outgoing traffic based on predefined rules. In web hosting, firewalls protect servers from unauthorized access, malicious attacks, and suspicious traffic patterns.
How Does Firewall Work?
Firewalls operate at different levels: network firewalls filter traffic based on IP addresses, ports, and protocols, while application firewalls (WAFs) inspect HTTP traffic content for threats like SQL injection and cross-site scripting. Most hosting environments use both types for defense in depth.
In a hosting context, firewalls are configured to allow legitimate traffic (web requests on ports 80/443, SSH on port 22) while blocking everything else. Tools like iptables, UFW, and cloud security groups let you define precise rules. Managed hosting providers typically include firewall configuration as part of their service, while VPS and dedicated server users must configure their own.