iSACA Cybersecurity Fundamentals Certification Practice Exam

What range of port numbers is considered 'well known'?

1. 49152 to 65535

2. 1024 to 49151

3. 0 to 1023

4. 256 to 512

The correct answer is: 0 to 1023

The range of port numbers classified as 'well known' is from 0 to 1023. These ports are designated for specific services and protocols, meaning they are reserved for well-known applications and processes. For instance, port 80 is used for HTTP, port 443 for HTTPS, and port 25 for SMTP. Well-known ports facilitate the identification of specific services, enabling standardized communication across the internet and ensuring that when a client attempts to communicate with a server, it knows which service it should address based on the port number being used. In contrast, the other ranges mentioned are categorized differently. Ports from 1024 to 49151 are known as 'registered' ports, typically assigned by IANA (Internet Assigned Numbers Authority) for user processes or applications. The range from 49152 to 65535 is referred to as 'dynamic or private' ports, which are usually ephemeral and can be used temporarily by applications when they initiate a connection. The range from 256 to 512 does not fit into any standard classification of port numbers.