The correct answer is B, as it identifies the type of attack performed by Thomas in the above scenario. Eavesdropping is a type of attack that involves intercepting and listening to the communication between two parties without their knowledge or consent. Thomas performed eavesdropping by sniffing communication between the administrator and an application server to retrieve the admin credentials. Option A is incorrect, as it does not identify the type of attack performed by Thomas in the above scenario. Vishing is a type of attack that involves using voice calls to trick people into revealing sensitive information or performing malicious actions. Thomas did not use voice calls but sniffed network traffic. Option C is incorrect, as it does not identify the type of attack performed by Thomas in the above scenario. Phishing is a type of attack that involves sending fraudulent emails or messages that appear to be from legitimate sources to lure people into revealing sensitive information or performing malicious actions. Thomas did not send any emails or messages but sniffed network traffic. Option D is incorrect, as it does not identify the type of attack performed by Thomas in the above scenario. Dumpster diving is a type of attack that involves searching through trash or discarded items to findvaluable information or resources. Thomas did not search through trash or discarded items but sniffed network traffic.

References: Section 2.2