A man-in-the-middle intercepts traffic between two parties — reading, modifying, or blocking the communication without either endpoint knowing.
Explanation
MITM attacks are famous as security threats — a malicious actor on the same Wi-Fi network reading your traffic. But MITM is also a legitimate technique in enterprise environments where the company installs a root certificate on managed devices, allowing the corporate firewall to decrypt, inspect, and re-encrypt HTTPS traffic. Without the root cert, TLS is designed to prevent MITM — the browser would show a certificate warning. Web proxies are not MITM in the security sense — the browser explicitly connects to the proxy, and the proxy fetches destinations honestly. But architecturally, a web proxy is a chosen middleman, which is why the operator's trust story matters.
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