Exam SK0-005 topic 1 question 27 discussion

21 - FTP 22 - SSH 23 - Telnet 53 - DNS 443 - HTTPS 636 - LDAPS There are 3 ports which not secure and need to close 21, 23, 53 but the server provide DNS inquiries, so we don't close port 53.

DNS can also use other ports for specialized purposes. For example, DNS over TLS (DoT) uses port 853, and DNS over HTTPS (DoH) typically uses port 443 to encapsulate DNS traffic within HTTPS That's why 53 is blocked

Then get a new scanner because it is not showing Ports 21 and 23

How could DNS Port 53 needs to be close where the question asking for DNS Port to be used ?

A - Why would you leave an unsecure FTP port open? C - Telnet is notorious for sending credentials over the network in plain text. If you close port 53 how will hosts on the network get name resolution?

No ftp or telnet allowed

A and C should be the best answer

AC Port 21 and File Transfer FTP is often thought of as a “not secure” file transfer protocol. This is mainly due to FTP sending data in clear text and offering an anonymous option with no password required. However, FTP is a trusted and still widely used protocol for transferring files Is port 23 secure? Port 23 – Telnet. A predecessor to SSH, is no longer considered secure and is frequently abused by malware.

53 is for DNS query, why we need to close it?