Tips for securing your SSH server

Protected Session

Article from Issue 241/2020
Author(s):

An SSH server facing the Internet will almost certainly be under attack, but a few proactive steps will help to keep the intruders away.

Secure Shell, better known as SSH, is a secure communication protocol used to execute commands on remote servers. SSH works on a client/server architecture. Data transferred through SSH is automatically encrypted using symmetric, asymmetric, and hashing algorithms. At receiving end, the data is automatically decrypted.

About 90 percent of system administrators use SSH to access their servers and configure them remotely. Users overwhelmingly prefer SSH over Telnet, an alternative communication protocol that is now considered insecure. SSH makes the data in transit more secure, but if you wish to secure an SSH server, you need to take some additional steps. Following are some measures that will help you protect your SSH server from attack.

Public Keys Instead of Passwords

The article on "System Hardening" elsewhere in this issue mentioned the benefits of using key authentication rather than passwords with SSH. Your password can be cracked by intruders, and you could end up getting hacked by a simple brute-force password attack. Here is a quick reprise on how to set up key-based authentication.

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