'Is it possible to create a filter before authentication process in WordPress?

I was trying to figure out if it is possible to filter the entered username/email address before the user gets authenticated and logged in.

This way users won't be able to login using previously defined usernames/emails using a specific frontend login form.

As we have changed the default login page URL hackers won't be able to find the default login form easily and get access to administrative accounts.

Is it possible, any ideas?

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