Which device protects an internal network from the Internet?

A router primarily forwards packets between different networks based on routing decisions, without deep security policy enforcement.

A firewall acts as a security barrier between a trusted internal network and an untrusted external network like the Internet, enforcing security policies by filtering traffic based on rules such as IP addresses, ports, and protocols to prevent unauthorized access and protect against threats.

An access point provides wireless connectivity but does not inherently protect the network from external threats.

A Layer 2 switch operates at the data link layer to forward frames within a local network and does not provide security against external network threats.