The nmap scan results show that Telnet (port 23) is open. Telnet transmits data, including credentials, in plaintext, which is insecure and should be disabled to enhance security.
Disabling unencrypted protocols (such as Telnet) reduces exposure to man-in-the-middle (MITM) attacks and credential sniffing. Telnet should be replaced with a secure protocol like SSH, which provides encryption for transmitted data.