How come we get referral traffic from Example.com?, SEO - referral traffic - spam Options

[simple-a]

We recently got a significant amount of referral traffic coming to our Simple [A] website from example.com. As example.com is a placeholder website with no external links on it, how come we’re getting traffic from example.com??

Is this a spambot faking the origin? And more importantly is there a way to avoid this (other than creating a filter for unwanted traffic?

Thanks