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Yes: file-change notifications can reveal activity through event timing, file paths, names, or event types, even when the observing process cannot read the files’ contents. The demonstrations discussed here do not mean an app can universally recover typed characters, read protected files, or spy remotely: they involve code running on the device, and the signal and prerequisites differ by operating system.
What a file-notification side channel reveals
Operating systems notify programs when files or directories are accessed or changed. A notification may expose metadata—such as when an event occurred, which path was involved, or whether a file was created or deleted—without exposing the file’s contents. That metadata can still indicate user activity.
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The Graz University of Technology researchers’ central qualification is that “the contents of these files are unknown.” Their demonstrations are controlled experiments with local observers, not evidence that a remote attacker can simply inspect a victim’s device. The researchers’ disclosure and their 2026 paper describe the methods and evaluation conditions.
What the demonstrations show on each platform
| Platform and mechanism | Observed signal and demonstrated inference | Important limits |
|---|---|---|
| Linux: file notifications on watched directories and special files | Events and timing. Watching /dev/input revealed keypress timing; monitoring /dev/pts revealed some terminal input updates. Timing patterns were also used for website fingerprinting. |
The input demonstration exposed timing, not the identity of each key. With terminal input, sudo password typing with feedback disabled did not generate the relevant notifications. |
Android: FileObserver |
File events and filenames in the demonstrated WhatsApp media-folder scenario, despite the ordinary app-visible storage view. Names, locations, and timing could indicate media type and whether content was sent, received, or deleted. | This does not establish that any app can see every other app’s private files. Results are not established across all Android vendors, versions, or messaging apps. |
Windows: ReadDirectoryChangesW on a drive root |
System file events could expose full paths, including paths associated with other users. Relevant Firefox storage paths could disclose website names, rather than requiring only statistical guessing. | The reported website-detection results are not interchangeable across browsers: the researchers reported stronger detection for Firefox than Edge, without establishing a single result applicable to both. |
How to read the study’s accuracy figures
The paper reports 93.1%–100% F1 for local Linux inter-keystroke timing classification across seven users, 100% F1 in its remote SSH timing experiment, and 87.9% F1 for top-100 website fingerprinting in an open-world setting. For Windows, it reports 97.8% F1 for top-1,000 website-visit detection. These are results on the researchers’ specific participants and evaluation sets, not success rates promised on arbitrary devices or browsing sessions. “F1” is a combined precision-and-recall measure; it does not mean the system identified that percentage of every keystroke or visit in ordinary use. The study also reports up to 0.21% CPU overhead and temporal resolution of 0.2–11.5 ms for its tested monitoring setup, not a universal cost or resolution.
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Can notifications reveal what someone types?
They can expose timing patterns in some Linux scenarios, but the demonstrated signal is not a transcript. The Linux research used timing between events to classify inter-keystroke patterns; it did not establish that the watcher directly learns which key was pressed. The SSH experiment likewise concerns timing, and the researchers note that sudo password entry with terminal feedback disabled did not create the relevant terminal notifications.
A separate KDE Plasma 6 / Wayland demonstration used access to /usr/bin/pkexec to anticipate a polkit authentication prompt and place a fake password window over it. That is a distinct UI-redress scenario requiring a process running as the same user in the graphical session; it should not be conflated with cross-user event monitoring. The disclosure describes the demonstration and its conditions.
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Can an app see WhatsApp media without storage permission?
In the researchers’ Android demonstration, an unprivileged app used FileObserver to receive notifications and filenames in the tested WhatsApp media scenario, even though it could not list the other app’s media folder through the ordinary storage view. The side channel was the notification metadata—not access to the media contents. Filename and event details could suggest the kind of media involved and whether it was sent, received, or deleted.
The result is specific to the demonstrated path. The disclosure does not establish the same behavior for every Android release, device maker, storage configuration, or messaging app, and it lists no Android fix. See the researchers’ platform disclosure for the stated scope.
Can another user monitor websites on Linux or Windows?
Linux: statistical fingerprinting
The Linux website result is a classification experiment: the observer uses notification timing patterns to infer a site from an evaluation set. The reported 87.9% F1 applies to top-100 website fingerprinting in the paper’s open-world setting. It is not direct disclosure of every URL visited, nor a guarantee for a different browser, machine, network, or site set.
Windows: paths can disclose names
For Windows, the researchers report that monitoring directory changes at a drive root with ReadDirectoryChangesW can expose full file paths for system events, including paths belonging to other users. In their Firefox example, relevant storage paths include website names, making this a different kind of signal from Linux’s timing-based fingerprinting. The paper reports 97.8% F1 for its top-1,000 website-visit detection evaluation, but that metric should not be generalized to all browsers: the researchers describe Firefox detection as substantially stronger than Edge detection.
What mitigations are available?
Linux: update, but do not assume complete remediation
The researchers identify CVE-2025-68788 as a partial mitigation that suppresses access/modify notifications on special files. Their disclosure lists fixed kernel lines including 5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.65, and 6.18.3. These version numbers do not guarantee that a distribution has delivered the fix in that exact form; check the kernel and security advisories for the Linux distribution in use. The researchers explicitly describe the mitigation as partial, not a complete fix for every notification side channel. Their disclosure explains the mitigation’s scope.
Windows: consult Microsoft’s access-check guidance
Microsoft documents access-check enhancements intended to prevent unauthorized file-path disclosure through directory change notifications. The researchers identify the EnforceDirectoryChangeNotificationPermissionCheck setting as a mitigation and say it is disabled by default. Before changing it across managed devices, administrators should follow Microsoft’s current instructions for applicable Windows updates, policy or registry configuration, and compatibility requirements: Microsoft’s access-check documentation. The sources do not establish one universally compatible deployment outcome for every enterprise environment.
Android: no fix is listed in the disclosure
The researchers’ disclosure does not list an Android fix, and it does not establish present-day patch status across vendors. Keep Android and apps updated, and avoid installing untrusted software; ordinary storage permissions alone should not be treated as proof that notification metadata cannot leak. That is a precaution, not a demonstrated platform-wide remedy.
What is known about real-world exploitation?
The researchers state, “We are unaware of any such case.” This reports their knowledge at the time of the disclosure; it is not proof that exploitation has never occurred. The evidence described here is from controlled demonstrations and evaluations, not confirmed operational attacks in the wild.
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