Over the 20 years since the introduction of the “Secure Socket Layer” (SSL) by Netscape, its descendants have become the security standard for all web browsers and much else. The original SSL protocols were soon built upon by the IETF into the non-proprietary “Transport Layer Security” (TLS) protocols, but many people use the term “SSL” to refer to mean either SSL or TLS. Indeed, the latest version of SSL (SSL 3) has now officially been deprecated and should rarely if ever be seen in practice, due to security issues. SSL/TLS is a network protocol that secures data communication between servers and clients via a combination of asymmetric and symmetric cryptography. It is most commonly used together with HTTP (where the client and web server are a web browser) however it is also to be found in other protocols, including SMTP where it can be used to encrypt mail as it is sent between mail relays.