Firewalls
A firewall is a network security device that monitors both incoming and outgoing network traffic and either permits or prohibits specific traffic based on predefined security rules. A firewall can be a physical device (hardware) or software. The following is a summary of different types of firewalls that can be installed as hardware or software:
- Packet filtering firewall: These firewalls compare each packet to established criteria and allow/deny packet traffic based on predefined rules. These firewalls work on Layer 3 (the network layer) of the OSI model.
- Circuit-level gateway firewall: These firewalls monitor TCP handshakes and established sessions to determine the legitimacy of the traffic. These firewalls work on Layer 5 (the session layer) of the OSI model.
- Application-level gateway firewall: These firewalls provide the most secure connectivity as they examine each layer of communication. These firewalls work on the application layer (Layer 7) of the OSI...
