I'm new to hosting a WordPress Multi-User site. I went live about a week ago and two people immediately created blogs. That was a surprise, as there's nothing to indicate one should do such a thing. I found the setting for accounts but no blogs, but am not sure what to do about the two already created blogs. (Eventually the site will host author's blogs, but we're not to that point yet.)
My question is, are these spam somehow? Or perhaps a security threat? What should I do to secure the site/domain when I open it back up for people to create blogs, and is there anything I should do to make sure the two that already exist aren't a threat?