Which of the following best describes a Sniffer?

A sniffer is accurately described as a program that monitors data traveling over a network. This tool captures packets of data that are transmitted over the network, allowing for analysis of the information being sent and received. Sniffers are often used for network troubleshooting, performance monitoring, and security analyses, such as detecting unauthorized access or data breaches.

In practice, network administrators utilize sniffers to understand traffic patterns, diagnose issues, and ensure that data flows efficiently across the network. Additionally, they can be used maliciously to intercept sensitive information, which underscores the importance of implementing security measures to protect against such unauthorized monitoring.

The other descriptions do not align with the function of a sniffer. Amplifying network signals pertains to devices like repeaters or amplifiers, while blocking network traffic relates to firewall functionality. Creating firewalls involves configuration and network security policies, which are distinctly different from the role of a sniffer.