The Transport Layer Security (TLS) protocol is probably the most important security protocol on the Internet. It is generally used for secure authentication and encrypted communication, specifically for e-commerce or online banking. Without TLS (or its predecessor Secure Socket Layer, abbreviated SSL), the Internet could not have developed in its recent form. After several successful attacks against TLS have been demonstrated in recent years, the Internet Engineering Task Force (IETF) was forced to issue a new, improved version of TLS. In this paper some important attacks against TLS (up to version 1.2) will be presented and the new version 1.3 regarding these attacks as well as its efficiency will be analysed.