What is a significant risk of a botnet?

The significant risk of a botnet lies in the abuse of compromised computers for harmful activities. A botnet is a network of infected computers, often referred to as "zombies," that are controlled by a malicious actor. Once a computer is part of a botnet, the owner may have no knowledge of its involvement. These compromised machines can be utilized for a variety of malicious purposes, including launching Distributed Denial of Service (DDoS) attacks, spam campaigns, or spreading malware, all of which can have devastating impacts on individuals, organizations, and internet infrastructure.

The other provided options do not accurately reflect the nature of botnets. Improved user connectivity and enhanced server performance suggest beneficial outcomes that are not associated with compromised systems. Increased system redundancy implies that additional systems are available to take over in case of failure, which is more of a risk mitigation strategy rather than a consequence of botnets. Hence, the correct answer highlights the malicious nature and real-world impacts of botnets on compromised computers.