Telnet (Terminal Network) is a network protocol that provides a command-line interface. Unlike SSH, Telnet does not have data encryption or data integrity verification, so any attacks that can be executed against the TCP protocol may be performed against this protocol.
The Telnet protocol is known to be used by the Mirai botnet.
Do not use Telnet services or switch to secure analogue SSH. The following safety measures should be taken if you continue to use it:
- Change passwords regularly, and make sure they are strong;
- Protect your device from bruteforce attacks;
- Block Port 23 of the TCP protocol from external networks;
- Limit Telnet services availability based on IP addresses, countries, etc.