A firewall is a security system that filters network traffic to allow or block connections based on predefined rules. It acts as a barrier between trusted and untrusted networks, helping protect systems from unauthorized access. Firewalls monitor incoming and outgoing packets to determine whether they match allowed patterns. They can be implemented in hardware, software, or cloud environments. Firewalls form a key part of network security for servers, applications, and internal corporate networks. Developers often interact with firewalls indirectly when configuring deployments, ports, or service access. Misconfigured firewalls can block legitimate traffic or expose sensitive services unintentionally.
how it works
Firewalls inspect network packets and apply rule sets that match attributes such as source IP, destination IP, port, or protocol. Packet filtering firewalls operate at low network layers, while application aware firewalls analyze higher level traffic like HTTP. Cloud providers offer virtual firewalls that control traffic between virtual machines or containerized workloads. Logging helps identify suspicious patterns, blocked requests, or attempted intrusions. Understanding firewall behavior is essential when diagnosing connectivity problems between services.