![]() ![]() SCP is similar, but for CoPying files, because the Unix file-copy command is generally called /bin/cp, and SFTP is named in much the same way. ![]() SSH loosely means, “connect Securely and run a command SHell at the other end”, typically for interactive logins, because the Unix program for a command shell is usually /bin/sh. The SSH protocol is also used in other popular client-server services including SCP and SFTP, short for secure copy and secure FTP respectively. Indeed, if you run the Windows SSH server and connect to it from a Linux computer right now, you’ll almost certainly be relying on the OpenSSH implementation at both ends. The OpenBSD team wanted to create a free, reliable, open-source implementation of the protocol that they and anyone else could use, without any of the licensing or commercial complications that had encumbered Ylönen’s original implementation in the years immediately after its release. OpenSSH soon followed, as we mentioned above, first appearing in late 1999 as part of the OpenBSD 2.6 release. It was an instant hit, and the protocol was quickly adopted by sysadmins everywhere. ![]() Ylönen’s SSH aimed to add a layer of strong encryption and authentication to each end of a Telnet-like session, creating a secure shell (that’s what the name stands for, if you’ve ever wondered, although almost everyone just calls it ess-ess-aitch these days). They could even set up an imposter server, lure you to it, and make it surprisingly difficult for you to spot the deception. …and, of course, your username and password at the start of the session.Īnyone on your network path could not only easily reconstruct your sysadmin sessions in real time on their own screen, but probably also tamper with your session by modifying the commands you sent to the remote server and faking the replies coming back so you didn’t notice the subterfuge. The giant flaw in Telnet, of course, was its total lack of encryption, so that sniffing out your exact terminal session was trivial, allowing crackers to see every command you typed (even the mistakes you made, and all the times you hit ), and every byte of output produced… Same familiar login system, cheaper connections, no need for dedicated data lines! Telnet was remarkably simple and effective: instead of connecting physical wires (or using a modem over a telephone line) to make a teletype connection to remote servers, you used a TELetype NETwork connection instead.īasically, the data that would usually flow back and forth over a dedicated serial connection or dial-up phone line was sent and received over the internet, using a packet-switched TCP network connection instead of a circuit-switched point-to-point link. ![]()
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