[Plugin: StopSpammers] definition of "bad cache"

I cannot seem to find a definition of “bad cache” anywhere. Bad cache on the server? in WordPress? in my browser? How can a cache be “bad”? And I have no idea how that could be effect spam.

Specifically, I installed Stopspammers 6.0.8 (then had to update to 6.0.9) today for the first time and it immediately showed me that “bad cache” was causing the majority of my spam, which manifests itself in a lot of junk in google analytics. I left all settings at the default settings.

My discussion settings are all unchecked except:
Allow link notifications from other blogs (pingbacks and trackbacks) .
Email me whenever anyone posts a comment, a comment is held for moderation
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I have no cache plugins installed. Active Plug-ins:
Contact Form 7
contact form 7 honeypot
contact form 7 mailchimp extension
Google analytics master
Mailchimp for wordpress Pro
Optimize database after deleting revisions
Stop Spammers Spam control
SpamReferrerBlock
Wordpress SEO

There are a few more inactive plug-ins but none are cache plugins.

So the specific question is what do I do to get rid of “bad cache” spam?
Generally, I am interested in learning what exactly this “bad cache” is …

Thanks for any help.