Spam users

I had 5 “spam” users register on my blog.

Both these options were on/checked:
Anyone can register
Users must be registered and logged in to comment

I just turned off/unchecked anyone can register when I read them.

New user registration on your blog <blog name>:

Username: yhgtfrty

E-mail: [email protected]

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New user registration on your blog <blog name>:

Username: iuytrtyui

E-mail: [email protected]

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New user registration on your blog <blog name>:

Username: kujyhtgrt

E-mail: [email protected]

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New user registration on your blog <blog name>:

Username: jhgfdfghe

E-mail: [email protected]

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New user registration on your blog <blog name>:

Username: wertgfdd

E-mail: [email protected]

those are the 5 e-mails. I know in phpbb (forum software) I can make it so users who register have to activate their accounts by clicking a link on an e-mail they received.