 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 secured. No one, except maybe the NSA, can decrypt it. Not really. This means that a person can securely login 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 tunneling, forwarding TCP ports, and X11 connections. SSH uses the client server model. Say you are 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 Maisie. Hello. Nice to meet you. She enjoys mocha half-calf latte as much as the next person. She especially likes to sit in the neighborhood coffee shop and write mystery novels. Maisie loves to write and feels comfortable sending her chapters to her editor over FTP. She's always done it like this. What Maisie isn't thinking about is that she is using the coffee shop's Wi-Fi and the network is not secured. So when Maisie hits send, Read can capture this data through a man in the middle attack. All that data is now reads to steal and publish. Maybe even make a blockbuster movie. Oh, no. Sitting at the next table over from Maisie is Will. He likes his coffee iced and his connections secured. Will has heard about eavesdroppers like Read, so he is extra careful when he uses public Wi-Fi. 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 routing it through his home server. SSH also supports password-based authentication that 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 SecureShell.