If someone is hacking your database you might try adding a trigger to your user table that can send you an email anytime a record is added for a specific user group
Here's a sample of a trigger checking for a column value on an insert operation.
CREATE TRIGGER upd_check BEFORE UPDATE ON user
-> FOR EACH ROW
-> BEGIN
-> IF NEW.usergroupid = 6 THEN
-> send yourself an email
-> END IF;
-> END;//
And here's a link to how to use a trigger to send yourself an email:
http://stackoverflow.com/questions/3...from-mysql-5-1
Now no matter how they access your database (directly , ftp or through vbulletin) you will be alerted immediately
It may be easier to have the trigger write the info to a text file then set up a cron job to actually send the email.
I haven't tested this yet but will so shortly