How to block SPAM Newsletter subscriptions

Last days somebody (or more likely some bot) is subscribing to newsletters with SPAM email addresses :(

I have no clue why somebody does this (please enlighten me) but more important how do I block it?

I have removed the Newsletter subscription box from the site (via a tickbox in Admin area) but it still continues.

I get like 20 fake subscriptions a day.

Any suggestions how to block this? And why did the removing of the Newsletter subscription box not help?

Thanks!!

I have the same problem, Did you get a solution?

https://www.nopcommerce.com/boards/t/20176/urgent-regarding-fake-customers-registration.aspx