TLSMITM

TLS MITM refers to a set of techniques in which a third party sits between a client and a server in a TLS connection, terminating the TLS sessions on both sides and potentially decrypting, inspecting, modifying, and re-encrypting the traffic. The intermediary, acting as a man in the middle, can view plaintext data and alter it before forwarding it to the server. This enables visibility into encrypted traffic while keeping the illusion of end-to-end transport, but it also breaks true end-to-end confidentiality and integrity.

Deployment often occurs in enterprise networks via security gateways, proxies, or security appliances that perform TLS interception for purposes such as data loss prevention, malware inspection, and compliance monitoring. It can also be abused by attackers to harvest credentials or alter communications.

Operation at a high level: the intermediary presents certificates to the client for the target server, signed by a trusted authority controlled by the intermediary. If the client accepts that trusted authority, the TLS connection is effectively terminated at the intermediary; the proxy then establishes a separate TLS session with the real server. This arrangement requires trust in the intermediary and proper certificate management.

Limitations include modern defenses such as certificate pinning, HSTS, and some TLS 1.3 features that hinder interception. Misconfiguration or weak handling can create new risks, including exposure of sensitive data if the proxy is compromised or improperly deployed.

Ethical and legal aspects vary; legitimate use requires clear policy and consent, while unauthorized MITM activity is illegal in many jurisdictions.