Backlink: reference-notes-readme
Modern operating systems no longer leverage telnet, but we still see it on almost every pentest on embedded devices, or legacy systems. The old school command line console access operates as a cleartext protocol and has largely been replaced by SSH.
Port: 23/TCP
Tools: Telnet, Netcat (nc), Ncat
Examples:
telnet 192.168.1.1
nc 192.168.1.1 23
ncat 192.168.1.1. 23