Which description best defines an intercepting proxy's role in testing?

• A. It forwards traffic without inspecting it.
• B. It blocks all unauthorized connections.
• C. It sits between the client and server and can inspect, modify, or replay traffic.
• D. It only works for FTP traffic.

Answer: (C)

An intercepting proxy sits between the client and the server and acts as a man-in-the-middle, allowing you to inspect, modify, or replay traffic during testing. This setup gives you full visibility into what the client sends and what the server returns, so you can pause or break traffic to study headers, parameters, and responses, and you can alter requests or responses to test input validation, session handling, and security controls. You can also replay captured traffic to see how the server handles repeated or altered requests, which helps test idempotence and vulnerability behavior. In practice, you’d use tools like Burp Suite or OWASP ZAP, often configuring the client to route through the proxy (and installing its certificate to inspect HTTPS traffic). It’s not just about forwarding traffic, it’s about actively inspecting and modifying it; it’s not a general firewall that blocks unauthorized connections, and it isn’t limited to FTP traffic.