Newsletter sign up Image verification

I have been getting a lot of bot created newsletter signups. I was hoping there was a way I can add Image verification to the sign up block. I had used the “Activation link” method think that this would give the bots an email address that they could abuse somehow. If I am mistaken on this please let me know. If so, how do I find the unactivated emails address. I do not use cs-carts mailing feature, just export list from the database. Thanks, David DeWitt cs-cart ver 2.1.1