Tonight, I came to a conclusion.
All of the people on my Forums with their field_1 (Biography) set to Man are spammers.
So.. to stop them signing up, I used
Add User to Primary Usergroup Based on Value of Custom Profile Field - vBulletin.org Forum by the wonderful Amykhar, setting the variables to field_1 and Man respectively.
To destroy them and eradicate their presence, I ran the following queries.
**BACK UP YOUR DATABASE BEFORE PROCEEDING** Code:
SELECT *
FROM `userfield` AS userfield
LEFT JOIN `user` AS user ON (userfield.userid = user.userid)
WHERE `field1` LIKE CONVERT( _utf8 'Man'
USING latin1 );
to see them.. then delete them.