Secure Shell
Secure Shell or SSH in short is an application layer protocol that helps in connecting and working with a remote machine. SSH replaced its predecessor Telnet which is not as secure as SSH and thus vulnerable to security threats. SSH works with the help of public key cryptography which is a popular cryptography mechanism that is widely used for encrypting and decrypting information passed over the network. SSH is widely used to connect to remote UNIX/Linux systems to configure and manage. While majority of UNIX/Linux systems come with SSH service and command line client to connect to remote, Putty is a widely used GUI based SSH tool for Windows (as well as for *nix systems with graphical support) that can help in connecting to remote machine through SSH. Even though SSH enables a secure communication between the client and the server, the configuration of the SSH service on the server is very important to effectively enable a secure connection. This blog article “HOWTO: Five steps to a more secure SSH” discusses the 5 important steps to enable a secure SSH (that makes it secure secure shell 
)
