Have you ever been in the situation that you wanted to SSH directly to a machine, but there has been some device in between that prevents it? Say you have a Linux firewall that protects your DMZ, and you have a boatload of machines behind it that you want to manage. There are all sorts of methods that are used to do so, and all have some level of annoyance.

The first and most simple solution is to SSH to the machine in the way, say the firewall. The firewall administrator can just set up one or more non-privileged accounts for users who need access to the machines behind it. This is a pain, of course - if you want to upload a file, you need to upload it to the firewall via sftp/scp, and then upload it to the target server. What a pain. And security-wise, you now have all these random firewall accounts running amok, probably not your favourite situation.

By Brian Hatch at Hacking Linux Exposed.

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