macOS baseline defenses are the security controls built into Apple devices before any third-party antivirus is installed. They include malware checking, code-signing and notarization checks, Gatekeeper restrictions on untrusted apps, XProtect signature updates, and other system safeguards that help block or warn about suspicious software.
These controls matter because they provide the first layer of protection against common threats, reducing the chance that a user can launch a known malicious file or install unsafe software. In real attacks, they force adversaries to work harder by using unsigned apps, social engineering, or fileless techniques that try to bypass simple detection. In defense, they buy time: even when a separate security product is used, baseline defenses help contain risk and create a starting point for scanning, cleanup, and phishing protection. They are not a complete substitute for good security hygiene or additional tools when needed, but they are the foundation of macOS malware defense.