What is Firewall?
Turkish: Firewall
A firewall filters traffic between devices and networks using rules, allowing approved connections while blocking suspicious or unauthorized access.
What is a Firewall?
A firewall is a security layer that accepts, rejects, or limits network traffic according to defined rules. It works like access control for a building: the organization decides which source can reach which service through which entry point.
How Does It Work?
Rule sets can evaluate IP address, port, protocol, direction, connection state, and sometimes application identity. For example, public traffic may be allowed only to port 443 for HTTPS, while a database port remains reachable only from the application server.
Basic packet-filtering firewalls inspect individual packets. Stateful firewalls track connection state. Next-generation firewalls may add application recognition, user policies, and threat intelligence. A WAF is a different layer because it focuses specifically on HTTP application traffic.
Risk and Protection
A firewall does not provide complete security by itself. A wrong rule, exposed admin panel, or unnecessary allowlist entry can increase the attack surface. For high-volume DDoS attacks, upstream protection, rate limiting, and CDN-level controls may be needed alongside firewall rules.
Good management uses least-privilege rules, closes unused ports, records rule changes, and reviews logs regularly.
Related Terms
DDoS is an attack that floods a service from many sources, requiring capacity, filtering, monitoring, and mitigation planning.
NAT (Network Address Translation)NAT translates private network addresses to public addresses or ports, allowing local devices to communicate across the internet.
Network SegmentationNetwork segmentation separates users, servers, and systems into controlled network zones to limit unauthorized access and attack spread.
Penetration TestingPenetration testing is an authorized security assessment that uses controlled attacks to find vulnerabilities in applications, networks, or infrastructure.
VLANA VLAN separates devices into logical network groups on shared hardware, isolating traffic and tightening access control.
VPN (Virtual Private Network)A VPN creates an encrypted tunnel between a device and a target network, protecting traffic and enabling private access.
WAF (Web Application Firewall)A WAF analyzes HTTP traffic at the application layer to filter SQL injection, XSS, malicious bots, and abusive requests.