Apache Kafka 0.9 introduced significant security enhancements, making it possible to operate Kafka as a central platform for streaming data with robust encryption, authorization, and authentication features. These improvements, which are part of Confluent Platform 2.0, include client authentication using Kerberos or TLS client certificates, a Unix-like permissions system for user data access control, encrypted network communication, and authentication requirements for broker and ZooKeeper interactions. The security features are backwards-compatible and disabled by default, allowing for easy configuration without necessitating code changes. Enabling these security enhancements involves generating TLS keys and certificates, configuring Kerberos principals, and setting up various security protocols and ports. Additionally, Kafka's security can be managed through its pluggable Authorizer and ACLs, which define user access permissions. The document also provides guidance on setting up TLS and SASL/Kerberos authentication for both brokers and clients, emphasizing the importance of proper configuration to ensure secure communication across the Kafka ecosystem.