How does a firewall protect against unauthorized access?

A firewall acts as a barrier between a trusted internal network and untrusted external networks, such as the internet. It monitors incoming and outgoing network traffic based on a set of defined rules. Here are some ways a firewall protects against unauthorized access:

1. Packet Filtering: The firewall examines packets of data that enter or leave the network and blocks those that don't meet the specified criteria.
2. Stateful Inspection: The firewall keeps track of the state of active connections and only allows packets that are part of a legitimate connection.
3. Proxy Service: The firewall acts as an intermediary for communication between internal and external systems, hiding the internal IP addresses and enhancing security.
4. Application Layer Filtering: The firewall inspects data at the application layer to block malicious content or control access to specific applications.

By implementing these security measures, a firewall helps prevent unauthorized access, protect sensitive data, and maintain the integrity of the network infrastructure.