What primary protection do LANs need against unauthorized access from outside sources?

Firewalls serve as a crucial line of defense in protecting Local Area Networks (LANs) from unauthorized access by external threats. A firewall acts as a barrier between the trusted internal network and untrusted external networks, such as the internet. It monitors and regulates incoming and outgoing network traffic based on predetermined security rules. By filtering potentially harmful traffic and blocking unauthorized users, firewalls help prevent intrusions and attacks on the internal network.

While encryption, authentication, and network monitoring are important components of a comprehensive security strategy, they do not primarily address the immediate threat of unauthorized access from outside sources in the same way that firewalls do. Encryption secures data during transmission, making it unreadable to eavesdroppers, while authentication verifies the identity of users and devices attempting to access the network. Network monitoring is essential for detecting anomalous activities and analyzing traffic patterns but does not prevent unauthorized access on its own. Together, these tools enhance overall security, but the firewall is specifically designed to prevent external unauthorized access.