It seems someone has been trying to hack into our continuum server. Please view the attached image. The users at the end having the name as nessus. Can anybody please provide an explanation for how a non admin can create users in continuum.

I am sure since day one, the continuum admin user has been locked with a strong password and all, I also checked, there is no such user called nessus in our unix server - solaris 10. I also do not think anybody would have had the insight to break into the derby db and insert new users directly into the tables.