Last
updated December 26, 2000 v4.33
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| Filemon
monitors and displays file system activity on a
system in real-time. Its advanced capabilities make
it a powerful tool for exploring the way Windows
works, seeing how applications use the files and
DLLs, or tracking down problems in system or application
file configurations. Filemon's timestamping feature
will show you precisely when every open, read, write
or delete, happens, and its status column tells
you the outcome. Filemon is so easy to use
that you'll be an expert within minutes. It begins
monitoring when you start it, and its output window
can be saved to a file for off-line viewing. It
has full search capability, and if you find that
you're getting information overload, simply set
up one or more filters.
Filemon works on NT 4.0, Windows 2000,
Windows 95, Windows 98 and Windows ME.
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| Simply run the Filemon
(filemon.exe) Windows NT/2000 Note: you must have
administrative privilege to run Filemon.
When Filemon is started for the first time
it will monitor all local hard drives. Menus, hot-keys,
or toolbar buttons can be used to clear the window,
select and deselect monitored drives (Windows NT/2K),
save the monitored data to a file, and to filter
and search output.
As events are printed to the output, they are
tagged with a sequence number. If Filemon’s
internal buffers are overflowed during extremely
heavy activity, this will be reflected with gaps
in the sequence number.
Use the Filter dialog, which is accessed with
a toolbar button or the Edit|Filter/Highlight
menu selection, to select what data will be shown
in the list view. The '*' wildcard matches arbitrary
strings, and the filters are case-insensitive.
Only matches shown in the include filter, but
that are not excluded with the exclude filter,
are displayed. Use ';' to separate multiple strings
in a filter (e.g. "filemon;temp"). Windows
NT/2000 note: because of the asynchronous
nature of file I/O, its not possible to filter
on the result field.
For example, if the include filter is "c:\temp",
and the exclude filter is "c:\temp\subdir",
all references to files and directories under
c:\temp, except to those under c:\temp\subdir
will be monitored.
Wildcards allow for complex pattern matching,
making it possible to match specific file accesses
by specific applications, for example. The include
filter “Winword*Windows” would have
Filemon only show accesses by Microsoft
Word to files and directories that include the
word “Windows”.
Use the highlight filter specify output that
you want to have highlighted in the listview output.
Select highlighting colors with Edit|Highlight
Colors.
Filemon can either timestamp events
or show their duration. The Options menu and the
clock toolbar button let you toggle between the
two modes. The button on the toolbar shows the
current mode with a clock or a stopwatch. When
showing duration the Time field in the output
shows the number of seconds it took for the underlying
file system to service particular requests.
Each time you exit Filemon it remembers
the filters you've configured, position of the
window and the widths of the output columns.
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Starting in version 4.1 Filemon is able
to monitor named pipe and mail slot file system
activity on Windows NT/2K. Named pipes are commonly
used as a communications mechanism in NT/Win2K
by core subsystems like the Local Security Authority
Subsystem (LSASS), and are used by DCOM. They
are also used by network components such as the
Browser service. To see named pipe activity with
Filemon select Named Pipes in the Drives
menu and perform an operation on a shared network
resource, or open an application such as Regedt32
that interacts with the security subsystem.
Mail slots are much less commonly used. If you
find an application that uses mail slots, please
let me know.
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| For the
Windows 9x driver, the heart of Filemon is
in the virtual device driver, Filevxd.vxd. It is
dynamically loaded, and in its initialization it
installs a file system filter via the VxD service,
IFSMGR_InstallFileSystemApiHook, to insert
itself onto the call chain of all file system requests.
On Windows NT the heart of Filemon is a
file system driver that creates and attaches filter
device objects to target file system device objects
so that Filemon will see all IRPs and FastIO
requests directed at drives.
When Filemon sees an open, create or close
call, it updates an internal hash table that serves
as the mapping between internal file handles and
file path names. Whenever it sees calls that are
handle based, it looks up the handle in the hash
table to obtain the full name for display. If
a handle-based access references a file opened
before Filemon started, Filemon will
fail to find the mapping in its hash table and
will simply present the handle's value instead.
Information on accesses is dumped into an ASCII
buffer that is periodically copied up to the GUI
for it to print in its listbox.
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Here
are some other monitoring tools available at Sysinternals:
- Regmon
- a Registry monitor
- Tdimon
- a TCP/IP monitor
- Portmon
- a serial and parallel port monitor
- PMon
- a process and thread monitor (NT/Win2K)
- Diskmon
- a hard disk monitor (NT/Win2K)
- DebugView/EE
- a debug output monitor
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| The following
serve as additional sources of information on the
Windows 9x file system:
These are source of information on the Windows
NT/2000 file system and/or Filemon:
- Inside Windows
2000, 3rd Edition by David Solomon and Mark
Russinovich, 2000
- "Examining The Windows NT File System,"
by Mark Russinovich and Bryce Cogswell, Dr.
Dobb's Journal, Febrary 1997
- "Inside NT Utilities", Windows NT Magazine,
February 1999.
- "Windows NT File System Internals,"by
Rajeev Nagar, O'Reilly and Associates, 1997
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Filemon Enterprise Edition, the commercial
version of Filemon available from Winternals
Software, extends the functionality of Filemon
with several powerful features, including the
ability to monitor remote systems and save output
to a log file as the output generates.
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In order to help us track its use, please
download through the link that represents the
operating system on
which you will use or mostly use Filemon.
Note that the zip files are identical, and Filemon
runs on either platform.
Download Filemon
(x86- 76KB) - you plan on using Filemon on Win9x
Download Filemon
(x86 - 76KB) - you plan on using Filemon on WinNT
Download Filemon
(Alpha - 92KB)
Download Filemon
Plus Source (353KB)
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