Which device monitors and controls network traffic based on established rules?

The device that monitors and controls network traffic based on established rules is a firewall. Firewalls are specifically designed to enforce security policies by examining incoming and outgoing traffic, allowing or blocking data packets based on predetermined security rules. They can be hardware-based or software-based and provide a robust layer of protection for private networks by preventing unauthorized access and ensuring that only legitimate traffic is allowed through.

Firewalls can operate at various levels of the OSI model, typically at the network layer (packet-filtering firewalls) or the application layer (stateful inspection or application-layer firewalls). Their ability to maintain and apply rulesets allows them to adapt to various threats and respond accordingly to suspicious activity, making them essential for network security.

Other devices like routers, switches, and access points serve different primary functions. Routers are mainly used to forward data packets between different networks and determine the best path for data. Switches operate primarily at the data link layer, directing traffic within a local area network (LAN) without necessarily endorsing security rules. Access points provide wireless connectivity to devices and manage local network traffic without the specific focus on security policy enforcement that firewalls possess. Thus, firewalls are uniquely suited to monitor and control network traffic in accordance with established security policies,