I have just discovered that someone has logged in and created a group on my site.
I cannot get rid of it using Delete Group.
It has nothing to do with my site and DOESN'T show up in my group listings BUT DOES show up in the sidebar widget so you can click on it.
How do I (a) get rid of it and (b) close the creation of groups to prevent it happening again. (This is not the idea as I wanted people to create their own groups WITHIN the community but it appears there is no way for the Admin to approve the establishment of a group - or is there a way to do it.