"IP address-based stream security" allows you to restrict or prohibit the listening of your radio to certain IP addresses. By extension, you can use this feature to make your radio private.
Block IP addresses
Allow IP addresses
To activate the IP address-based stream security:
- Click on the 3 dots found next to the name of your radio station
- Go to Settings > Security
- Enable "IP address-based stream security"
BLOCK IP ADDRESSES
Select “I want to block” when you:
- Want listeners using a particular IP address to be blocked from your radio
- Want listeners using the NON-listed IP addresses to have access to your radio
Example: Here, I want to block IP address "56.16.27.133". This means that people using that IP address will not have access to my radio station. 
ALLOW IP ADDRESSES
Select “I want to allow” when you:
- Want listeners using the listed IP addresses to have access to your radio
- Want listeners using the NON-listed IP addresses to be blocked
Example: Here, I want to allow IP address "56.16.27.133". This means that only people using that particular IP address have access to my radio station.
To sum up, "block" corresponds to a black list of IP addresses and "allow" corresponds to a white list.