What does SSH stand for?
SSH stands for Secure Shell. Encrypted remote command-line access and file transfer on TCP port 22, replacing Telnet, which sends everything in plain text. Key-based authentication is stronger than passwords; disable root login and limit who may connect.
SSH gives an administrator an encrypted command-line session on a remote system, by default on TCP port 22. It replaced Telnet, which sends everything, passwords included, in clear text. The user can authenticate with a password or, better, with a key pair. On first contact the client shows the server's host key fingerprint and remembers it, which protects later sessions against an impostor server. The same protocol carries file transfer, as SFTP and SCP, and can forward other ports through the encrypted connection.
SSH in practice: an example
An administrator manages Linux servers and switches from her laptop. She connects with SSH and signs in with her private key and its passphrase. One morning the client warns that a server's host key has changed. She stops and checks before continuing, because that warning is what an interception attempt would look like.
What SSH is confused with
SSH vs Telnet: what is the difference?
Both give a remote command line. Telnet, on TCP port 23, sends everything unencrypted. SSH, on TCP port 22, encrypts the whole session.
SSH vs RDP: what is the difference?
SSH provides a text-based shell and is the norm on Linux and network devices. RDP provides a full graphical desktop and is the norm on Windows. What RDP stands for
Which exams cover SSH?
SSH is on the official CompTIA acronym list for two of the four exams covered here.
- Network+ N10-009: 1.0 (Networking Concepts); 3.0 (Network Operations).
- A+ 220-1201 and 220-1202: 220-1201 2.0 (Networking); 220-1202 4.0 (Operational Procedures).
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. A technician must replace Telnet for managing switches with a protocol that encrypts the session. Which one should be used, and on which default port?
- SSH on TCP port 22
- FTP on TCP port 21
- HTTP on TCP port 80
- TFTP on UDP port 69
Show the answer
A. SSH on TCP port 22. SSH is the encrypted replacement for Telnet and listens on TCP port 22 by default. The other protocols transfer files or web pages and do not encrypt.
2. Which SSH authentication method is the most resistant to password guessing?
- A short shared password
- Public key authentication
- No authentication
- The default vendor password
Show the answer
B. Public key authentication. With key authentication there is no password for an attacker to guess over the network. The private key stays on the client.
Sources: RFC 4251: The Secure Shell (SSH) Protocol Architecture; RFC 4253: The Secure Shell (SSH) Transport Layer Protocol; NIST glossary: Secure Shell. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.