CREST Practitioner Security Analyst (CPSA) Practice 2025 – All-in-One Guide to Mastering Exam Success!

Port 135 is associated with Windows Remote Procedure Call (RPC) and serves as the End Point Mapper (EPM). This port is crucial for service aggregation and communication between different network services on Windows operating systems. When a client makes a call to a service that uses RPC, it first contacts the EPM service on port 135 to determine the dynamic ports used by the requested RPC service. This design allows for more flexible communication and port management in Windows environments, enabling services to communicate without needing to know the exact port numbers in advance.

The other ports mentioned—88, 110, and 123—are typically associated with different protocols. Port 88 is used for Kerberos authentication, port 110 is the default port for the Post Office Protocol version 3 (POP3) for email retrieval, and port 123 is used for the Network Time Protocol (NTP), which synchronizes clocks over a network. These ports serve different purposes and are not involved in the functions of Windows RPC.