Telnet is an insecure protocol that transmits data in cleartext over the network. This means that anyone who can intercept the network traffic can read the data, including the username and password of the server administrator. A packet capture tool is a software or hardware device that can capture and analyze network packets. An attacker can use a packet capture tool to steal the password and use it to install malicious software on the server. Reference: https://www.comptia.org/content/guides/what-is-network-security

Disabling remote logins to the NAS likely involved turning off SSH instead of modifying the configuration file.
This would prevent users from using SCP to transfer files to the NAS, even though the data is still viewable from the users' PCs. Source: TechTarget