The operating system is the beating heart of any computing device—and securing it properly lays the groundwork for all other defenses. In this episode, we focus on OS-level security enhancements like Group Policy Objects (GPOs) for centralized control in Windows environments, and Security-Enhanced Linux (SELinux) for mandatory access control enforcement in Linux systems. We explore features such as account lockout thresholds, password policies, audit log configurations, and secure boot implementations that prevent tampering with the OS before it fully loads. We also highlight how role separation, user privilege restrictions, and kernel integrity checks protect against privilege escalation and unauthorized modifications. Securing the operating system isn’t glamorous, but it’s essential—because if an attacker controls the OS, they control everything. Well-configured, updated, and monitored OS settings reduce the window of opportunity for compromise dramatically.