Step 1: Update the WhatsApp app
Step 2: Open the app and go to settings
Step 3: In Settings, click on account, then privacy, then groups
Step 4: Tick on the radio box next to nobody, my contacts or everyone to change the settings, and you are done
Enabling nobody in privacy settings for a group would prompt the person inviting you to the group to send a private invite through an individual chat, giving you the option of joining the group. The invite will be valid for three days, before it expires and automatically rejects the invite request.