If you create and store your own passwords for websites and apps and any are weak (for example, they’re easily guessed or used multiple times), iPod touch identifies them for you automatically. iPod touch can also securely monitor your passwords and alert you if they appear in known data leaks.
Go to Settings > Passwords > Security Recommendations, then tap an account.
In the Security Recommendation section, tap > Passwords > Security Recommendations, then turn Detect Compromised Passwords on or off.