What Gives?

Okay, WordPress people, I have a question.  From time to time I get likes on my posts from a blog which, when I click on the link to check it out, gives the message that the blog has been deleted.  Also, occasionally I get followers who seem a bit, shall we say, sketchy.

How can I tell if these are actual bloggers or if they’re bots or something?  And is there any way to prevent being followed by ‘not actual people’?

Please advise.