Explanation:
multi-factor authentication (MFA)
In Microsoft Entra ID (formerly Azure AD), Security defaults are a baseline of recommended identity protections that, when turned on, automatically apply tenant-wide. Microsoft's guidance explains that security defaults "help protect your organization with preconfigured security settings" and specifically require that "all users register for Azure AD Multi-Factor Authentication." When enabled, the defaults enforce MFA challenges for users and admins during risky or sensitive operations, and they block legacy authentication protocols that can't satisfy modern MFA requirements. Microsoft further notes that security defaults "provide basic identity security mechanisms... such as requiring multi-factor authentication for all users and administrators." These controls are designed to raise the overall security posture without custom policy design, which is ideal for small and medium organizations or any tenant that hasn't yet implemented Conditional Access. Therefore, when you enable security defaults, MFA is enabled for all Azure AD users, driving strong authentication as the default and reducing account-takeover risk stemming from password-only sign-ins.

Explanation:

In Microsoft's Security, Compliance, and Identity guidance, multi-factor authentication (MFA) is based on combining independent categories of credentials to verify a user. Microsoft describes the three factor types as:
something you know (knowledge), something you have (possession), and something you are (inherence). A password is explicitly categorized as "something you know," because it relies on a secret the user memorizes and types during sign-in. MFA improves security by requiring two or more of these distinct factors-e.g., a password (know) plus a phone approval or hardware token (have), or a biometric like Windows Hello (are).
Using factors from different categories mitigates common attacks such as password spray, credential stuffing, and phishing, because compromising one factor (for example, the password) does not grant access without the second, unrelated factor. Microsoft recommends enabling MFA broadly and pairing passwords with stronger possession or inherence methods to achieve a measurable reduction in account compromise risk. Therefore, in the MFA model used by Microsoft Entra ID (Azure AD), a password is considered something you know.

Explanation:
https://learn.microsoft.com/en-us/azure/ddos-protection/ddos-protection-overview
https://learn.microsoft.com/en-us/azure/ddos-protection/ddos-protection-features