A Security Engineer at a medium-sized accounting firm has been tasked with discovering how much information can be obtained from the firm's public facing web servers. The engineer decides to start by

Cross-site scripting involves injecting malicious client-side scripts into web pages to attack other users, not passively reading server response headers.

Banner grabbing is a reconnaissance technique where an attacker connects to a service and reads the response headers or initial connection banner to identify the software type and version running on the server. The output reveals 'Server: Microsoft-IIS/6', which discloses the web server software and version - exactly the intelligence banner grabbing is designed to collect.

SQL injection involves inserting malicious SQL statements into input fields to manipulate backend database queries, which is unrelated to reading HTTP headers via netcat.

A Whois database query retrieves domain registration and ownership information from a registry, not HTTP response headers from a web server.