In FrontDesk Master, when you add a guest to your Blacklist, the system adds it automatically to our Global Blacklist

This means that when a property which uses FrontDesk Master blacklists a guest, you will receive an information about blacklisted guest when he makes a reservation in your property. 

For example, if Hostel ABC blacklisted a guest and this guest is now in my property, the guest will appear as blacklisted (reservation circled in red):

You will see the basic information about the guest (Gender, Country, ID and Email), who and when blacklisted this guest (in which property, which user), the reason of the blacklist and recommendation:

You can search guests in Global Blacklist when you enter to your local Blacklist. Enter the email or ID number of the guest and check if he is blacklisted in the Global Blacklist:

See also:

How to unblacklist guest?

How to blacklist guest?

Where can I check if guest is blacklisted?