Spammers often subscribe to newsletters, but they can be traced through their URL.  We can prevent them from registering by finding these URLs and disallowing access.

  1. Login to the admin of your site.
  2. Go to: Components >> jNews >> Lists. 
  3. Edit the list under consideration. On the edit page, go to "Front-end Management" tab, and set "List Subscription Access" to none.
  4. Save the page.