Batch spam user accounts deletion

Hi. I got a service without a recaptcha and with about a half of million user accounts. I know about mergeUsers.php and i deleted all users with frame or iframe, and some other strings in url, interests and other searcheabe fields, but now I still have a half of millinon accounts, and only about 2000 deletions.

Is it possible to filter|search user profiles by “biography” field? Or may be any other ways? I am not very good in mysql, but i can run sql query and understand a result. Help me to get usernames, for example with “iframe” string in biography field.

Application Version - OJS