Systems that use the NTFS file system can govern who has execution rights to what files.

That's the good news. Here's the bad news: removable drives such as CD/DVD-ROMs or USB keychain drives usually aren't formatted with NTFS, making it harder to prevent people from running programs on such media.

If blocking the use of all removable drives isn't practical, then what is?

The folks at BeyondLogic.org have come up with an interesting solution -- a filter driver for 32-bit Windows called Trust-no-exe 3.04 (

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http://www.beyondlogic.org/solutions/trust-no-exe/trust-no-exe.htm).

The freeware driver works at the file system level, intercepting all calls to execute programs from any mounted file system, and matches those calls against a list of allowed drives and paths. If someone attempts to run a program from a pathname that isn't allowed, an error dialog pops up.

Trust-no-exe doesn't rely on file extensions or even the DOS-compatible drive letter to determine what's legitimate and what's not, so it is not easily circumvented. It examines the kernel-level routines that attempt to create a process and load it into memory, so it doesn't rely on file types or other "high-level" mechanisms for figuring out what's legit and what's not.

Once installed, the program can be managed through a Control Panel icon. You can add explicitly allowed or explicitly denied pathnames, create a custom "access denied" message and even govern the behavior of executables run from other computers (making it easy to "push" settings through a network). The program can also be used with third-party programs such as Novell's ZenWorks to have custom allow/deny lists "pushed" into the Registry key where it keeps its settings.

One thing you need to remember is if you are using a mixture of 16- and 32-bit programs, you may need to specify paths to 16-bit programs using an 8.3 file path. (Make sure 8.3 filename generation is enabled for the volume in question.) Also, you can't remotely install Trust-no-exe on Windows XP Home (although you can install it locally).


Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter. Check out his Windows 2000 blog for his latest advice and musings on the world of Windows network administrators -- please share your thoughts as well!

This was first published in December 2004

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