Why is a firewall necessary in computer security?

A firewall is a critical component in computer security because it serves to prevent unauthorized access to the computer and its network. By monitoring and controlling incoming and outgoing network traffic based on predetermined security rules, a firewall acts as a barrier between a trusted internal network and untrusted external networks, such as the internet. This function is essential in establishing a secure environment, protecting sensitive data from potential threats, and blocking malicious attacks.

The other options, while related to computer performance and maintenance, do not accurately describe the primary role of a firewall. For instance, boosting processing power and increasing hardware lifespan are not functions of a firewall; rather, they pertain to the performance and longevity of the computer's hardware components. Similarly, serving as backup storage is a completely different aspect of data management and does not align with the fundamental purpose of a firewall in maintaining network security.