A firewall is a security system that monitors and controls network traffic based on predefined rules. It acts as a barrier between trusted internal networks and untrusted external ones, such as the internet, deciding which traffic to allow or block. In modern enterprises, firewalls are essential for preventing unauthorised access, data breaches, and cyberattacks.
How It Works
Firewalls inspect incoming and outgoing data packets to determine whether they comply with security policies. Traditional firewalls relied mainly on source and destination addresses or ports, while next-generation firewalls (NGFWs) add deep packet inspection, intrusion prevention, and application-level visibility. They can identify specific applications, users, and threats in real time.
Business Relevance
For organisations, firewalls form the first line of defence in a layered security strategy. They protect networks, data centres, and cloud environments by controlling exposure to external threats. Firewalls also help businesses maintain compliance with standards such as ISO 27001 and PCI DSS, which require robust network segmentation and traffic monitoring.
In hybrid and multi-cloud architectures, enterprises often deploy firewalls as virtual appliances or cloud-native services. Solutions from vendors like Cisco, Palo Alto Networks, and Fortinet integrate advanced analytics and AI to detect and block evolving threats.
Types of Firewalls
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Packet-filtering firewalls: Examine packets based on IP addresses and ports.
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Stateful inspection firewalls: Track the state of active connections for context-aware filtering.
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Next-generation firewalls (NGFWs): Combine traditional filtering with intrusion prevention and application control.
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Cloud firewalls: Deployed as software-based services to secure cloud and hybrid workloads.
Considerations
A firewall is most effective when paired with other defences such as endpoint security, intrusion detection, and security information and event management (SIEM) systems. Regular policy reviews and updates are crucial to prevent misconfigurations, which remain one of the leading causes of firewall breaches.
