Hi @mochi93
I think your fake sign-ups are from bots. Have you tried these two methods yet?
- Enable reCAPTCHA for your store: https://help.shopify.com/en/manual/online-store/setting-up/preferences
- Require double opt-in for subscribers: https://help.shopify.com/en/manual/promoting-marketing/create-marketing/customer-contact-information#enable-double-opt-in-for-subscribers