Windows explorer search handling from our Hook Method

General
1

We would like to handle the Windows explorer search as soon as user entered a single character. We found there is no single Win32 API to which we can hook into. Request you to share if we can handle Windows explorer search operation through Windows driver

The use case is as follows:

Windows Explorer provides a search box for the currently opened folder.

The user can type any string or pattern or a single character into the search box, and Windows OS will perform the default search operation.

In our use case, if the user opens a mapped network folder (hosted on our Linux server) and initiates a search, we want to intercept and handle the search operation ourselves, returning the list of matched files.

Currently, Windows handles the search operation on its own, opening and reading file contents one by one from our server.

This impacts performance significantly, especially for large files. We are not able to attach the Wireshark packet log

We intend to intercept the Windows Explorer search operation so that the search string entered by the user can be sent to our Linux server from our application. The server will then process the query and return the matched file list, which we would display directly in the Explorer view. This approach aims to avoid the current behavior where Windows opens, reads, and closes each file individually resulting in performance degradation, especially with large files.

We would appreciate your guidance on how to achieve this.

Specifically, we are looking for ways to hook into the Windows Explorer search operation, as we are currently unsure of the best mechanism to do so. Thank you very much.

2

Thank you for the detailed use case. Intercepting Windows Explorer’s search operation is indeed a challenging task, especially since there’s no public Win32 API or documented interface that allows direct hooking into the search box behavior of Windows Explorer. However, considering your requirements and constraints, here’s a technical breakdown of your options and best potential approaches—including whether a Windows driver can help.

Problem Recap

  • You want to intercept Windows Explorer search input, ideally as soon as the first character is typed.
  • The search occurs in a mapped network drive, backed by a Linux server (likely via SMB or NFS).
  • You want to short-circuit Windows’ default file content scanning, and instead send the query to your Linux server to return matching file results.
  • You want to display the custom results in the Explorer window, similar to default search.

Possible Approaches

1. Custom Shell Namespace Extension (SNE)

This is the most feasible and clean solution:

  • You create a custom shell extension that replaces Windows Explorer’s behavior for a specific folder (e.g., your mapped drive).
  • You implement your own IShellFolder, IShellView, IQueryInfo, etc.
  • When the user types into the search box, your custom SNE gets the query and can intercept it immediately, send it to your Linux server, and display results like normal search.
  • Explorer will render the folder view and search results based on what you return.

Pros:

  • Full control over the view and search.
  • No need to fight Explorer’s internals or undocumented behavior.
  • Official, documented, and extensible via COM interfaces.

Cons:

  • Complex to implement (but this is the “official” method).
  • Shell extensions are written in C++ and require COM expertise.

Microsoft Docs - Shell Namespace Extensions

2. File System Filter Driver (Not recommended for search interception)

A Windows file system minifilter driver (written with the Filter Manager framework) can intercept:

  • IRP_MJ_CREATE
  • IRP_MJ_READ
  • IRP_MJ_QUERY_INFORMATION

But:

It cannot intercept high-level Explorer UI events like “search input” directly.
It’s too low level – by the time Explorer hits the file system, the search has already been initiated.
However, it can help you detect search patterns (e.g., rapid open/read/close) and possibly block them, though with extreme care.

So unless you want to block search behavior entirely, this is not the correct place to intercept and redirect searches.

3. Network Provider Redirector (Custom SMB or WebDAV handler)

If you’re using a custom network drive, you could provide a custom redirector (via Network Provider interface or WebDAV server) that:

  • Emulates a network filesystem (like SMB/WebDAV),
  • Parses incoming directory listing/search requests (e.g., FindFirst/FindNext),
  • And responds with filtered results.

This means Windows never performs content-based search—it will only list files that match your filtered result.

This works best if you can fully control the network protocol layer, e.g.,:

  • A custom SMB server on the Linux side with tailored responses.
  • A custom WebDAV server where you control the responses.
    Example: Dokan (user-mode file system for Windows), or WinFsp + custom handler.

4. Explorer UI Hooking (Last resort / risky)

Using techniques like UI automation, DLL injection, or low-level SetWindowsHookEx(), you could theoretically hook into:

  • The search box control in Explorer,
  • Intercept WM_CHAR/WM_KEYDOWN events,
  • Detect input and intercept the search logic.

But:

This is extremely fragile and version-specific.
Likely to be blocked by Windows security features like AppContainer, Defender, etc.
Not a viable long-term solution.

Use only for proof-of-concept or R&D, not for production.

Why You Can’t Intercept Search via a Win32 API or Driver Directly

Windows Explorer does not expose a public API or driver IOCTL that indicates “a user started a search in this folder.” It’s tightly integrated with:

  • Windows Search Indexer,
  • Shell UI components,
  • File system access patterns (open/read/close).

So by the time a driver sees activity, it’s already too late to redirect the user’s intent.

Recommended Solution Path

For your specific use case, here’s the most practical architecture:

  1. Do not use SMB directly; instead, implement a custom namespace extension or use a custom file system (via WinFsp, Dokan, or WebDAV).
  2. Inside the namespace extension or file system handler:
  • Detect when a user initiates a search.
  • Immediately send the query to your Linux server.
  • Retrieve matching file names.
  • Return only those files in the directory listing.

This makes Windows Explorer think the folder only contains the matching files, thus avoiding any content-level reads.

Summary

Method Intercepts Search Input Explorer Integration Feasibility Recommendation
Shell Namespace Extension Yes Full integration Complex but official Best option
File System Filter Driver No Too low-level High complexity Not suitable
Custom Redirector (SMB/WebDAV) Partial (by filtering queries) Moderate Complex server-side Good alternative
UI Hooking / DLL Injection Maybe Very fragile Risky and unsupported Not recommended