WhatsApp just added th Group privacy setting in its app, it enables you to control who can add you to a WhatsApp group.
Here's how to access it馃憞馃憞
Open WhatsApp on your phone, and go to Settings > Accounts > Privacy.
*Tap on Groups, and select the option that suits you best. The first one will prompt the user adding you to send an invitation that you can approve:
~ Nobody ( this stops anyone from adding you to a group without an invitation)
My Contacts ( Only your contacts can add you to a group without an invitation)
Anyone ( Anyone can add you to a group without an invitation)