Which of the following tools is primarily used for vulnerability scanning?

Nessus is primarily used for vulnerability scanning, making it the correct choice. It is a well-known security tool designed to identify vulnerabilities in systems and network configurations by scanning for known weaknesses, misconfigurations, and compliance violations. Nessus performs comprehensive assessments, allowing organizations to prioritize and remediate identified vulnerabilities based on their severity.

In contrast, Wireshark is a network protocol analyzer used for packet capturing and detailed network traffic analysis. It provides insights into the data packets traversing a network but does not focus specifically on vulnerability detection.

Burp Suite serves as a tool for web application security testing. It is designed to identify security vulnerabilities in web applications by allowing penetration testers to interactively analyze and manipulate web traffic but is not primarily a vulnerability scanner.

Putty, on the other hand, is a terminal emulator used for remote access to computers through protocols like SSH and Telnet, and it does not perform vulnerability scanning tasks.

Thus, Nessus stands out as specialized for vulnerability scanning, making it the appropriate option among the provided tools.