Welcome to an overview of Secure Shell, SSH. Today we will learn the basic
definitions and importance of SSH.
So what is SSH? SSH is a unix based command interface and network protocol.
A network protocol is a set of rules that tells your computer how to send data
from one place, say from your computer, to another server.
If you send data over telnet or FTP it goes as plain text and is unencrypted.
This means it is vulnerable. Someone could see it and take your information
So what can you do to protect your data?
Well, unfortunately it isn't possible for one person to secure the entire network.
But, what is within their control, is to secure a channel on that network.
SSH secures access to remote computers. It can transmit data, commands, and even files.
Because it is a cryptographic network protocol, it is secure.
No one, except maybe the NSA, can decrypt it.
This means that a person can securely log in from any remote location like a coffee shop.
Some of the key benefits of SSH is that it provides confidentiality and
integrity of data even on an unsecured network.
It can be used anywhere in the world.
It can be used on different platforms.
In fact, all major platforms such as Windows, Mac, Linux, iOS.
SSH is most commonly used in Linux. It can connect from one
platform to another and all of these connections can be secured with a
password or an asymmetrical key system.
SSH also supports tunnelling, forwarding TCP ports, and x11connections.
SSH uses the client server model.
Say you're at a coffee shop on a non-secured network,
SSH allows you to tunnel through to your home server and surf the web from there.
This is Maisy. "Hello nice to meet you"
She enjoys mocha half-caf lattes as much as the next person. She especially likes
to sit in the neighborhood coffee shop and write mystery novels. Maisy loves
to write, and feels comfortable sending her chapters to her editor over FTP. She's
always done it like this.
What Maisy isn't thinking about is that she is using the coffee shop's WiFi
and the network is not secured.
So when Maisy hits "Send",
Reid can capture this data
through a man-in-the-middle attack.
all that data is now Reid's to steal, and publish, and
maybe even make a blockbuster movie.
Sitting at the next table over from Maisy is Will.
He likes his coffee iced and his connections secured.
Will has heard about eavesdroppers like Reid.
So, he is extra careful when he uses public wifi.
Will is reading up on his favorite football teams. He is trying to decide who
should be his quarterback for his fantasy football league. He doesn't want anyone
getting his notes, so he decides to log on using SSH.
This way he can secure his data by running it through his home server.
SSH also supports password based authentication that is is encrypted by
automatically generated keys. It uses a public key to encrypt the message and a
private key to decipher it.
Without SSH, an attacker could imitate the legitimate server side, ask for the
password and obtain it in what is called a man in the middle attack.
However, this is possible only if the two sides have never authenticated before.
As SSH remembers the key that the server side previously used.
The SSH client raises a warning before accepting the key of a new, previously unknown
server.
Password authentication can be disabled.
What software is required to run SSH?
If you're running Linux or Mac, SSH is built into the terminal.
On Windows, you will need to install a third-party client. For example, PuTTy.
So, that covers software on the client -side.
On the server,
you'll need to have a daemon or service application running.
A daemon is a program
that runs continuously as a background process.
Congratulations! You've just completed an overview of Secure Shell.