[Osiris]

Microsoft Port Reporter is a handy application that can be installed as a service in Microsoft Windows to log port usage data. The application logs port activity on Windows XP, Windows 2000 and Windows 2003 server systems. A preciser description would be that it logs which ports are used, which process is using the ports, which modules are loaded by the process, if the process is a service and which user account is running the process.
The application can be used to make a in depth analysis of open ports on the system. The service has to be started manually after which it automatically begins to write logfiles in the directory \system32\LogFiles\PortReporter. The service creates the three logfiles:
PR-INITIAL-*.log

The PR-INITIAL log file contains data that the Port Reporter service collects about the ports, processes, and modules that run on the computer when the Port Reporter service is started. The user context that each process is running under is also logged.

PR-PORTS-*.log

The PR-PORTS log file contains summary data about TCP and UDP port activity on the computer.

PR-PIDS-*.log

The PR-PIDS log file contains detailed information about ports, processes, related modules, and the user account the process uses to run.

Take a look at the Microsoft Knowledge Base article “Availability and description of the Port Reporter tool” for further information.