Remote accessTCP 23 Cleartext by default
Port 23: Telnet
Telnet
Legacy remote terminal protocol with no encryption. Still found on network devices, IoT and OT equipment.
Secure alternative: SSH (22)
How attackers abuse it
- Credentials and every command readable on the wire.
- Default passwords on IoT devices - the Mirai botnet spread mainly through Telnet.
How to defend it
- Disable Telnet and use SSH.
- Block port 23 at the perimeter and change all default credentials.
Exam tip
Any exam scenario that mentions Telnet is usually asking you to replace it with SSH.