An administrator would like to scan for open ports on the subnet and determine if any vulnerable applications are listening. Which of the following tools would the administrator MOST likely use?

Ping uses ICMP echo requests to test basic host reachability; it cannot scan for open ports or identify vulnerable applications.

Nessus is a comprehensive vulnerability assessment tool that actively probes hosts on a subnet to discover open ports, identify the services running on them, and match those services against a database of known vulnerabilities. This makes it the appropriate tool for both port discovery and vulnerability identification in a single scan.

IMAP (Internet Message Access Protocol) is an email retrieval protocol used by mail clients to access mailboxes; it is not a network scanning or security assessment tool.

Telnet is an unencrypted remote terminal protocol that can manually connect to a single port on a single host to check if it is open, but it cannot scan a subnet or identify vulnerable applications automatically.