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Non-Standard Port

What: Non-Standard Port

In the context of computer networking and IT security, a "Non-Standard Port" refers to any network port number that is used by services and applications outside the range of well-known or commonly assigned port numbers as defined by the Internet Assigned Numbers Authority (IANA). Standard ports are typically those below 1024, known as well-known ports (e.g., HTTP on port 80, HTTPS on port 443). Non-standard ports generally refer to those above 1024 and are often used for user-defined processes or services.

How: Usage of Non-Standard Ports

  1. Configuration: Services can be configured to listen on non-standard ports either through their configuration files or startup command-line options. For example, configuring an Apache server to listen on port 8080 instead of its default port 80.

  2. Programming: When developing networked applications, developers may choose non-standard ports to avoid conflicts with well-known services or when standard ports are restricted by firewall policies. This is often specified in the service's code where the socket binds to a port.

  3. Networking Tools: Tools like netstat, lsof, or ss can be used to identify which services are running on non-standard ports on a system.

Where: Implementation and Detection

Non-standard ports are implemented at the application layer within the OSI model. They primarily involve configurations within server software or client applications that communicate over the network.

Detection of non-standard port usage can occur through:

  • Network Monitoring: Using tools like Wireshark or tcpdump to capture and analyze network traffic.
  • Port Scanning: Tools like Nmap scan a range of IP addresses to discover active services running on non-standard ports.
  • System Auditing: Employing auditing tools that log service configurations and network activities.

Why: Reasons for Using Non-Standard Ports

  1. Avoidance of Standard Port Limitations: Some environments restrict access to standard ports due to security policies, requiring services to operate on non-standard ports.

  2. Security through Obscurity: Some administrators use non-standard ports as a basic method of hiding services from rudimentary scans, which may target only well-known ports.

  3. Conflict Resolution: On machines where multiple instances of a service might run, or different services need similar resources, non-standard ports help in avoiding conflicts between multiple services.

  4. Testing and Development: During development phases, applications might run on non-standard ports to not interfere with production environments or standard service operations.

Using non-standard ports is both a practical necessity in complex environments with multiple applications and a rudimentary security measure against less sophisticated threats. However, it's essential to note that using non-standard ports should not be relied upon as a primary security measure; it does not replace robust authentication, encryption, and comprehensive network security practices.