Default or built in mechanism in Mac OS

 Mac OS includes a number of built-in security features to protect users and their data. Some of the default security mechanisms provided in Mac OS are:

Firewall: Mac OS includes a built-in firewall that helps prevent unauthorized access to your computer. The firewall can be configured to allow or deny incoming connections from specific applications or services.

FileVault: FileVault is a built-in encryption feature that can encrypt the entire contents of your Mac's hard drive. This helps protect your data if your Mac is lost or stolen.

Gatekeeper: Gatekeeper is a feature that helps protect your Mac from malware by only allowing apps from the App Store or identified developers to be installed.

XProtect: XProtect is a built-in antivirus feature that helps protect your Mac from known malware threats.

Safari security features: The Safari web browser included with Mac OS includes a number of built-in security features, such as the ability to block pop-ups, disable Java and Flash, and warn you if you are visiting a potentially dangerous website.

Keychain Access: Keychain Access is a password management tool that is built into Mac OS. It securely stores your passwords and other sensitive information, and can also generate strong passwords for you.

System Integrity Protection (SIP): System Integrity Protection is a security feature that is designed to prevent malicious software from modifying important system files and directories.

Overall, Mac OS includes a number of built-in security features that are designed to help protect your Mac and your data from a variety of threats.