Security Best Practices by Operating System

Windows Server

Use Windows Server Update Services (WSUS) for centralized patch management
Enable and configure Windows Defender
Implement Group Policy Objects (GPOs) for consistent security settings
Enable BitLocker for drive encryption
Use Windows Event Forwarding for centralized logging
Disable unnecessary services and roles
Implement Network Level Authentication (NLA) for Remote Desktop Services
Configure and use Windows Firewall with Advanced Security

Detailed Windows Server Security Checklist

Linux (General)

Keep the system updated using package managers (apt, yum, dnf)
Use SELinux or AppArmor for Mandatory Access Control
Configure and enable a host-based firewall (iptables, ufw, firewalld)
Implement secure SSH practices (key-based authentication, non-standard port)
Use sudo for privileged access instead of root login
Enable and configure system auditing (auditd)
Use disk encryption (LUKS)
Implement process isolation using cgroups and namespaces

Detailed Linux Security Checklist

FreeBSD

Keep the base system and packages updated using freebsd-update and pkg
Use jails for service isolation
Implement and configure PF (Packet Filter) firewall
Enable and configure security event auditing
Use GELI for disk encryption
Implement secure boot with UEFI and verified boot
Use Capsicum for capability-based security
Configure and use mandatory access controls (MAC)

Detailed FreeBSD Security Checklist

Pro Tip:

While these best practices provide a solid foundation for securing each operating system, always consult the official documentation and security guides provided by the OS vendor for the most up-to-date and comprehensive security recommendations.

Cross-Platform Security Considerations

Implement network segmentation to isolate different OS environments
Use centralized logging and monitoring solutions compatible with all your OS types
Implement consistent access control policies across all platforms
Conduct regular vulnerability assessments and penetration testing for all OS environments
Develop and maintain cross-platform incident response procedures
Provide security awareness training that covers best practices for all used operating systems