I recommend configuring Azure AD Conditional Access and using smart account lockout in Azure AD B2C.

Azure AD Conditional Access allows you to set policies that determine when and how users can access your application. By integrating Azure AD Conditional Access with user flows and custom policies, you can define rules that ensure only authenticated users can access the application, and you can also set up multifactor authentication for additional security.

Smart account lockout in Azure AD B2C is a feature that helps protect against brute-force attacks by temporarily locking out accounts after a certain number of failed login attempts. This can help prevent unauthorized access to the application by preventing attackers from guessing login credentials.