One of the most interesting Windows kernel internals is "PsActiveProcessHead", the global doubly-linked list that connects every live "EPROCESS" through "ActiveProcessLinks". Process creation inserts into this list, process exit removes from it, and kernel debuggers can walk it to enumerate active processes. Security researchers love it because many classic rootkits used DKOM (Direct Kernel Object Manipulation) to unlink their "EPROCESS" from "PsActiveProcessHead", effectively hiding a running process from tools that trusted the list. Understanding "PsActiveProcessHead" is often the first step into Windows rootkits, process hiding, forensic detection, and kernel debugging.