5000 users I don’t need…

I have a blog I have not serviced for more than a year.

Now I suddenly start getting emails about new users. I go there to look and I see I’ve now got more than 5000 user accounts.

Obviously spammers or whatever you call them.

I thought I had the board set so’s no one could become a user without I got notification but apparently not.

So I need to get rid of them. I don’t find a bulk delete option – only page by page – and even if/when I do I guess a blind bulk delete would delete my own accounts so that’s no good.

How should I proceed? p.s. it needs an update, too, and of course it advises me to backup before doing that. Pointless backing up while it has 5000 false accounts, I think.