We recently switched our company website and database to wordpress. For security, we didn't transfer most of our users. Right now I'm going through our Wordfence firewall logs to find all the users that have tried logging in with a username or email that currently doesn't exist. Nearly all these users listed are in our old database that I can easily transfer over.
I was going through hooks but am kinda lost. Is there an easy method to get an email alert sent to the admin when someone tries to login with invalid credentials? Ideally, I'm only looking for usernames that don't already exist. I rather not get emails for users who simply mistype their password.