Authentication logs are records of events related to user authentication on a computer system, network, or application, typically containing information about login attempts, success or failure, and sometimes additional details such as the user's identity, IP address, and authentication method. Monitoring authentication logs is crucial for detecting security threats, login errors, trends, and compliance issues, as well as identifying potential vulnerabilities in third-party tools. Effective monitoring involves centralized logging, regular review, user behavior analytics, multi-factor authentication, log retention and archiving, access controls, and incident response planning. To make the most of authentication logs, it's essential to include relevant data such as who, what, when, how, and where, structured in a format like JSON for easier analysis, and visualize and analyze data using prebuilt dashboards like New Relic's observability platform.