NERC Critical Infrastructure Protection (CIP) Practice Exam

The command used by auditors to identify open ports is 'netstat -a -n -o'. This command is a networking utility that displays active network connections, listening ports, and other associated information about the network interfaces on a system.

The parameters provided with this command enhance its functionality:

- The '-a' option shows all connections and listening ports, giving a comprehensive view of the network status.

- The '-n' option displays the addresses and port numbers in numerical form rather than resolving them to their hostnames, which allows for quicker output, especially on systems with a large number of connections.

- The '-o' option displays the owning process ID associated with each connection, which is useful for identifying which application is using a particular port.

In contrast, the other choices do not represent standard or widely recognized commands for identifying open ports. They may imply a similar functionality, but they either don't correspond to commonly used commands or simply don't exist as recognized networking tools in standard operating systems. Hence, the effectiveness and reliability of 'netstat -a -n -o' in auditing network ports make it the correct answer.