This multi brute force concept was first discovered by Bang Djon which was then applied to Bang Djon's FBBF which is available for Command Line Interface based and has been widely used in Indonesia.
This attack is a large-scale attack with a small risk, a collection of Facebook user account IDs entered will be tried to login with the password you mentioned.
The impact of the damage obtained is very small, for example a multi brute force attack:
Think of this key as a password and 10 other locked rooms are a collection of Facebook IDs, then you try to open all the locked rooms with the key you have, you try each door alternately with the key and some of the doors open because your key matches key owner of the room.
So this is proof of the multi brute force concept.
Python 3.x
apt-get update && apt-get upgrade
apt-get install python git
pip install requests
git clone https://github.com/BlackHoleSecurity/FMBrute
cd FMBrute
python fmbrute.py