Plan-B for SPAM ?

I've been using D7 for about 3yrs now , one of my top items in my wish list I was hoping to see gone by now is the unauthorized users who somehow get to my site w/o approval. You can call it SPAM or whatever it is. I call it D7 SECURITY HOLE. I am running D7.1.4 and I gave up hope.  Instead I would like to make my site completely private if possible.

In other words, I'd like to remove  [ join.php ] and replace it with a page that says: email us at members@gmail.com to become a member, and after I validate their email address, I will give them access to my site.

Is this doable ? if so, please provide steps how to do this..

Thank you !

Please note, as soon as I posted this thread (above), I came across this great free Mod posted by @gameutopia
http://www.boonex.com/forums/#topic/Add-A-Member-In-Dolphin-Administration-Module.htm 

which will allow me to add a new member via Admin - I can't thank Gameutopia enough for sharing this great Mod with us. My solution is 70% resolved now, I just need to know if I can make my site completely private & I maintain the members manually using this great  Mod.

Thank you. 

trident is having this feature ..maybe they will add in d 7.2 ..

and u right ..there should be more feature to prevent spam users .. altest filtering of email provider should be there..

or like inform the admin if different user login from same ip address ..

I believe we can switch the site to invite-only based.. Could someone shed some lights please & explain how it can be done..

Thanks. 

Admin Panel => Settings => Advanced Settings => Profiles. You'll need to use the Share button in your profile's action block, or click the Invite a Friend link in the footer to send the invite code to somebody.

And speaking of security holes, 7.1.5 was released, which addresses one. I recommend you upgrade to it ASAP. 

However, the invite a friend script as shipped with Dolphin is not secured.  You can search the forums here to learn more.