The classic Sysinternals Portmon has not been updated in many years. Because it relies on a legacy kernel driver, it frequently encounters "Access Denied" or "Unable to start driver" errors on modern operating systems like Windows 10 or Windows 11. These OS versions have stricter security policies regarding kernel-mode driver signing, often preventing unsigned or legacy drivers like Portmon's from loading.
Portmon is used to observe how software interacts with hardware ports. It is essentially a "sniffer" for I/O requests. Common scenarios include: portmon