John works as a Network Security Professional. He is assigned a project to test the security of with netcat and sends a bad html request in order to retrieve information about the service on the host.

Banner grabbing is a reconnaissance technique where an attacker connects to an open port and sends a crafted or malformed request to elicit a service response that reveals the server software, version, and OS. Using netcat to send a bad HTTP request and reading the resulting response headers is a textbook example of active banner grabbing performed during the pre-attack information gathering phase.

War driving involves physically driving around with wireless scanning equipment to detect and enumerate nearby Wi-Fi networks, which is unrelated to probing a specific host with netcat.

Eavesdropping is the passive interception of communications between two parties without their knowledge, not the active probing of a service with crafted requests.

Sniffing is the passive capture of network packets as they traverse a shared medium or network segment, not the active technique of sending requests to a host to read its banner.