Which of the following ports is a secure protocol?

Port 443 is the standard port for HTTPS (Hypertext Transfer Protocol Secure). HTTPS is a secure protocol because it uses an encryption layer, either Transport Layer Security (TLS) or its predecessor Secure Sockets Layer (SSL), to protect the confidentiality and integrity of data exchanged between a web browser and a server. This encryption prevents eavesdropping and man-in-the-middle attacks. The other listed ports are associated with protocols that are fundamentally insecure by design, as they transmit data, including authentication credentials, in clear text.

A. Port 20 is the data transfer port for the File Transfer Protocol (FTP), which is inherently insecure as it transmits credentials and data in clear text.

B. Port 23 is used for Telnet, a remote terminal protocol that sends all communication, including usernames and passwords, in unencrypted clear text.

D. Port 445 is used for Server Message Block (SMB). While modern versions can be configured for encryption, the protocol has a history of significant vulnerabilities and is not considered secure by default.

1. Internet Assigned Numbers Authority (IANA). (2024). Service Name and Transport Protocol Port Number Registry. This official registry explicitly defines port 443 for https (http protocol over TLS/SSL)

while listing port 20 for ftp-data

port 23 for telnet

and port 445 for microsoft-ds.

2. Rescorla

E. (2000). RFC 2818: HTTP Over TLS. The Internet Society. Section 2.1

"HTTPS Connection Initiation

" specifies that "HTTP/TLS is assigned the reserved port 443." The entire document is dedicated to defining the secure operation of HTTP over a TLS-encrypted channel.

3. O'Connor

T. (2010). Violent Python: A Cookbook for Hackers

Forensic Analysts

Penetration Testers and Security Engineers. Syngress. Chapter 2

"Penetration Testing with Python

" discusses the insecurity of FTP and Telnet

stating

"FTP is an insecure protocol that sends the username and password in cleartext... Telnet is another insecure protocol that sends all of its traffic in cleartext." (This is a peer-reviewed publication used in academic security courses).

4. Dordal

P. L. (2019). An Introduction to Computer Networks. Loyola University Chicago

Department of Computer Science. Chapter 9.7

"Secure Sockets Layer / Transport Layer Security

" page 423. The text explains

"TLS is the standard for encrypting TCP connections. The best-known application is HTTPS

for secure web transactions; the server listens on TCP port 443."