Random influx of newsletter sign ups

Over the last week, I have suddenly started receiving dozens of newsletter sign ups every day. While I’d love to think new fans have discovered our site out of the blue, I am pretty sure that’s not the case. Most of the content is outdated and even at its peek traffic levels the site never got this many signups.

This appears to only happen in the newsletter block form and all they submit is their email address.

Any clues?

I'm having the same issue as of 2 days ago. They are all weird email addresses. And with several people following the question, something may be up. Following.