Define "botnet".

A botnet is best defined as a network of compromised devices controlled by cybercriminals. This typically involves a collection of internet-connected devices such as computers, smartphones, and IoT devices that have been infected with malicious software. The cybercriminals control these devices remotely, allowing them to execute various harmful activities without the consent of the device owners.

Botnets are often employed for purposes such as launching Distributed Denial of Service (DDoS) attacks, distributing spam emails, stealing personal information, or mining cryptocurrencies. The scale and impact of botnets can be significant, and understanding their operation is crucial for recognizing and mitigating the risks involved in network security.

The other choices do not accurately encapsulate the characteristics of a botnet. A network of secure servers suggests a controlled and protected framework, which does not align with the malicious intent behind botnets. Monitoring network traffic pertains to analyzing data flows within a network rather than operating compromised devices. Lastly, network access control refers to methods used to restrict unauthorized access to network resources, which is unrelated to the concept of a botnet.