Which of the following is NOT a function of a firewall?

A firewall is primarily designed to control and monitor network traffic based on predetermined security rules. Its main functions include filtering packets, logging network activity, and monitoring incoming and outgoing traffic to enforce security policies.

Filtering packets involves inspecting and determining whether to allow or block specific data packets based on criteria such as source IP address, destination IP address, ports, and protocols; this helps prevent unauthorized access and protect network integrity. Logging network activity enables administrators to track and audit traffic, which is essential for identifying potential security threats and ensuring compliance with policies.

While caching web content can improve the speed and efficiency of a web service by storing copies of frequently accessed web pages, this function is not typical of a firewall. Such web caching is more aligned with proxy servers or web caches, which specialize in delivering content more quickly to clients rather than enforcing security policies. Therefore, it is not a function that a firewall usually performs.