Why Telnet died and SSH stayed
Passwords in the clear on port 23. Encryption on 22. Old printers still have not heard.
Telnet was how you opened a remote terminal. You typed a password. The password rode the network as readable text. Anyone on the same wire could collect it. SSH showed up in 1995 and did the same job with encryption and keys. Telnet did not vanish because people hate change. It vanished because the cleartext login was indefensible.
Why this still comes up
Old printers, old switches, old power strips, and cheap cameras still speak telnet. The manual says to open port 23. The password is on a sticker. Search engines still find those banners. So do worms.
If a device only offers telnet, put it on a guest network with no path to your files, or replace it. Do not “just for a minute” expose port 23 to the internet. There is no minute. The scanners are already looping.
FTP in the clear is the same family of mistake. SFTP and FTPS exist. SCP exists. Use them. The file you thought was boring is often a password list you forgot was in the folder.
SSH is not automatic safety
SSH can be set up badly: password login, root login, ancient protocol versions, a key without a passphrase on a stolen laptop. The protocol is the floor, not the ceiling. Still, it is a floor telnet never had.
When a vendor’s “cloud camera” talks to the mothership, that is not telnet, but the lesson is cousin to it: know whether the path is encrypted, and who holds the other end. A camera that only works through a random server in another country is a camera you should not aim at a crib.
The habit
Prefer SSH. Prefer HTTPS. Prefer anything that refuses to send a password as text. If the only option is the 1980s protocol, the device is the problem. Treat it like a tool that cannot keep a secret, because it cannot.