Spam Subscriber Accounts

In the last two days about a hundred users have subscribed to my site (https://pakistaniaat.net). All of them look like spam email addresses. Noticing this, I did the following:
1) Added a plug in that requires a capthca enabled form.
2) Removed the subscribe widget from my sidebar
3) Have now removed all front-end registration links.
4) Changed my WP password as well as my hosting password.
5) Reinstalled my theme

But I still keep getting new spam subscriptions. What else do I need to do? I would be grateful for any help.