Why should firewalls be used both at the host and network level?

Using firewalls at both the host and network levels is essential for a comprehensive security posture, which is best represented by the layered defense approach. Layered defense, often referred to as defense in depth, emphasizes implementing multiple security controls at different layers or levels to reduce vulnerabilities and risks.

Host-level firewalls serve to monitor and control incoming and outgoing traffic specifically for that device, effectively protecting it from threats that may already exist within the network. This is crucial because even a well-secured perimeter can be compromised, making host firewalls vital for individual device security.

Network-level firewalls act as barriers that filter traffic entering or exiting the network. They are designed to regulate external access to the network and mitigate threats that originate from outside sources, such as internet-based attacks.

Combining both types of firewalls enhances security exponentially. If one firewall fails or is bypassed, the other remains in place to provide a level of protection, ensuring a more robust defense against a wider range of threats. Thus, the adherence to the principles of a layered defense and the complementary functions of host and network firewalls solidify the necessity for their dual implementation.