Transport layer security (TLS) was introduced in 1999 to address serious vulnerabilities inherent in all versions of the Secure Sockets Layer (SSL). It is highly recommended that you secure your MongoDB installations with TLS 1.1 or above (covered later in this book). Once you have configured your mongod instances to use TLS, all communications are affected. These include communications between clients, drivers, and the server, as well as internal communications between members of a replica set and between nodes in a sharded cluster.
TLS security depends on which block cipher algorithm and mode are selected. For example, the 3DES (Data Encryption Standard 3) algorithm with the Cipher Block Chaining (CBC) mode are considered vulnerable to attack even in TLS version 1.2! The Advanced Encryption Standard (AES) algorithm and Galois Counter Mode (GCM) are considered a secure combination, but are only supported in TLS versions 1.2 and 1.3 (ratified in 2018). It should be noted...
