Ma, Is That You? 
Bibi, Azeem, Juzer and Thei Thei are having a meeting in their secret meeting place.
They hear a voice at their door. "Hello beta, it’s Ma! I brought snacks for you and your friends. Please open the door."
"You don’t sound like Ma," says Thei Thei. "What’s the secret knock?"
BAMBAMBAM "That’s not the right knock. Sorry, we can’t let you in!" says Azeem.
ROOOAAAR "I will get in one day!" shouts the monster from behind the door.
A few moments later…
"Hello beta, I bought a new game for your secret club! Please let me in!"
"What’s the secret knock?" asks Juzer.
"That’s the correct knock!" says Bibi.
"It is?" gasps the monster, "I mean, of course it is. Now let me in!"
"First show us your secret club card," says Azeem.
The monster slips a card under the door.
"Sorry, wrong card!"
The monster bangs on the door. "I’ll get in soon!" she cries.
A while later, there’s another knock at the door.
"I found a puppy for you," says the monster. "Please open the door!"
"What’s the secret knock?" asks Bibi.
"That’s correct!" says Bibi.
"Why wouldn’t it be? "First show us your Now let me in!" cries secret club card," the monster. says Azeem.
The monster slips a card under the door.
"That’s the right card," says Thei Thei. "Now show us your handprint. Place your hand against the window pane."
THUMP! A large, furry paw with long, sharp nails appears on the glass.
"That’s not Ma’s hand. Go away!" say the four children.
"ARRRRRR!" replies the monster, shaking her fist. "I would have gobbled you up if it wasn’t for your passwords!"
A few minutes later, there is one more knock at the door…
It’s the right knock.
A piece of paper slips under the door. It’s the correct secret club card.
Then—THUMP!—a hand print appears against the glass of the window.
"That’s Ma’s hand!"
Thei Thei swings open the door. It’s Ma, holding a tray full of mithai!
How do Thei Thei, Bibi, Juzer and Azeem keep their clubhouse safe? Thei Thei, Bibi, Juzer and Azeem use three ways of checking to make sure that their visitor is actually Mummy. This method of making sure that a person is who they claim to be is called authentication. It is often used in security systems so that the wrong person cannot get hold of important information that does not belong to them.

Since the four children use three steps to confirm the identity of their visitor, their method is known as multi-factor authentication (MFA).

MFA ensures that there is more than one level of security to protect important information like emails, social media profiles, bank accounts, etc. So although the monster passes the first two tests by cheating, the third test still stops her from getting into the clubhouse.
