![]() ![]() Whenever it sees calls that are handle based, it looks up Hash table that serves as the mapping between key handles and registry When Regmon sees an open, create or close call, it updates an internal Services, is merely one example of this capability in action. Regmon, which obviously hooks just the Registry-related It is possible to intercept and replace, augment, or monitor NT system To find the address of the NT function that will handle the request.īy replacing entries in this table with pointers to hooking functions, ![]() Passed in a machine register, and indexes into a system service table This handler takes a system call number, which is Software interrupt handler in NTOSKRNL.EXE (the core of the Windows NT When a user-modeĬomponent makes a privileged system call, control is transfered to a We developed for NT called system-call hooking. On Windows NT the Regmon loads a device driver that uses a technique Routines, so Regmon catches all registry activity taking place on a Programs, Win32 applications, or device drivers, are directed at these On VxD service hooking for more information) to insert itself onto theĬall chain of 16 registry access functions in the Windows 95 kernel Uses VxD service hooking (see our May 1996 Dr. It is dynamically loaded, and in its initialization it The heart of Regmon on Windows 9x is in the virtual device driver, ![]() Likewise, Regmon another predecessor is similar: Periodically copied up to the GUI for it to print in its listbox. Information on accesses is dumped into an ASCII buffer that is Handle-based access references a file opened before Filemon started,įilemon will fail to find the mapping in it hash table and will simply Handle in the hash table to obtain the full name for display. Whenever it sees calls that are handle based, it looks up the Serves as the mapping between internal file handles and file path Open, create or close call, it updates an internal hash table that Objects to target file system device objects so that Filemon will seeĪll IRPs and FastIO requests directed at drives. On Windows NT the heart of Filemon is aįile system driver driver that creates and attaches filter device IFSMGR_InstallFileSystemApiHook, to insert itself onto the call chain Initialization it installs a file system filter via the VxD service, On there's a short explanation about how FileMon, one of ProcMon's predecessors, works.įor the Windows 9x driver, the heart of Filemon is in the virtualĭevice driver, Filevxd.vxd. So it doesn't have to inject anything in other processes. It loads a virtual driver on startup which does the monitoring on a low-level. ![]()
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