WindowsSpyBlocker: telemetry rules built from captured Windows traffic

What WindowsSpyBlocker actually blocks, and for whom

Windows telemetry is not one endpoint. It is a shifting set of hostnames and IP ranges that Microsoft services contact for diagnostics, advertising identifiers, and feature telemetry. A static blocklist written once goes stale, and a blocklist written from guesswork blocks the wrong things. WindowsSpyBlocker's stated approach is to capture and interpret network traffic with a set of tools, then create rules based on the interactions between services and the source or destination of that traffic, sorted by assignment. The rules are therefore a byproduct of observation, not of someone reading a Microsoft document.

The audience is narrow and technical: Windows administrators and privacy-focused users who are comfortable applying firewall rules, editing a hosts file, or pointing a DNS resolver at a blocklist. The README calls it an application written in Go and delivered as a single executable. There is no installer wizard described, no tray icon, no background service. You run it, it helps you generate or apply rules, and you live with the consequences on that machine. If you want a tool that silently protects a family laptop, this is the wrong shape.

Capture, classify, generate: the rule pipeline

The mechanism is a pipeline with three visible stages. First, capture: the project's documentation describes collecting network traffic on a Windows host using a set of tools, which the repository topics hint at (wireshark and sysmon appear among them). Second, classification: each observed connection is judged by which Windows service initiated it and where it went, and the result is sorted into a rule category. Third, generation: those categories become the files under the data directory, which the executable can apply to the system.

The Go module graph supports this reading. The dependencies include miekg/dns for DNS handling, 0xrawsec/golang-evtx for parsing Windows Event Log data, and go-ole for Windows COM access. Those are the libraries you would reach for if you were correlating DNS queries with event log entries. The repository also carries a data directory, a docs directory, and a chocolatey directory, which is consistent with a project whose real product is the rule data and whose executable is the delivery mechanism.

One consequence of this design deserves stating plainly: the quality of the rules is bounded by the quality of the capture session. A service that changes its endpoints after the capture was taken will not be covered until someone captures again. The README does not describe an automatic update channel for rules.

Installing WindowsSpyBlocker and applying a first rule set

The README points to https://crazymax.dev/WindowsSpyBlocker/ for documentation and download, and the badges indicate a Chocolatey package named windowsspyblocker. The README does not spell out the install command, and no other repository file gives one, so the package page is the place to confirm the exact syntax before you run anything. Treat installation and rule application as separate steps: the README does not document what the package does to your firewall or hosts file on its own.

Otherwise, download the single executable from the releases page. The repository's top-level entries include main.go plus architecture-specific files (main_386.go, main_amd64.go, main_arm.go, main_arm64.go), which tells you the release artifacts are per-architecture and you should pick the one matching your CPU. The README gives no command-line flags, so the safest first move is to launch the executable and read the menu before changing anything.

Before applying a rule set, look at what you are about to install. The rule data lives under the data directory in the repository, and the same files ship with the binary. Read the file for the mode you intend to use and check whether its entries match services you actually rely on. Only then apply it, and note that the README does not document a rollback command, so capture your current firewall and hosts state first if you need a way back.

Where the rule sets will bite you

The most common failure mode for this class of tool is over-blocking. Because rules are derived from observed traffic, a hostname that serves both telemetry and a legitimate function will appear in the block list, and blocking it breaks the legitimate function. The README does not claim any allowlist review step, so the responsibility sits with you: read the rule file before applying it.

A second limitation is temporal. The most recent release listed is 4.39.0 from 2022-05-16, and the last push to the repository was 2026-09-09. A push is not a release, and the README and release list give no indication that a newer binary exists. If you are running a Windows build from after that release, the endpoints in the shipped rule data may be incomplete. The project's own method implies the fix is to run a new capture session and regenerate, which is work you have to do yourself.

A third case: this is the wrong tool on a managed corporate machine. Firewall and hosts changes there will either be reverted by group policy or will break management agents whose endpoints happen to sit in the blocked ranges. WindowsSpyBlocker assumes you control the host.

Compared with W10Privacy and Hardentools

W10Privacy and Hardentools attack the same problem from the settings side. They present toggles for Windows features, scheduled tasks and privacy options, and they change the operating system's own configuration so the telemetry is not generated in the first place. WindowsSpyBlocker does not touch those settings. It leaves the services running and cuts the network path, which means the telemetry attempt still happens and may still be logged locally, but the data does not leave.

The practical difference shows up when something breaks. If a settings-based tool disables a feature and that feature was load-bearing, you re-enable it in the same interface. If WindowsSpyBlocker blocks a hostname and a service silently degrades, you have to identify the blocked entry and remove it from the rule file. That is more work, but it is also more transparent: the rule file is a text artifact you can diff, version and review, which is not true of a registry change made by a GUI toggle. Choose based on whether you want the telemetry suppressed at the source or the traffic stopped at the boundary.

Maintenance cost and the MIT licence

The maintenance model is the weak point. Rules do not update themselves through any mechanism the README describes. Keeping coverage current means re-running the capture and classification workflow, which requires the tooling the project names (wireshark and sysmon appear in the repository topics) and a Windows machine you are willing to instrument. Budget that as periodic work, not a one-time install.

The project is MIT licensed, which permits commercial use, modification and redistribution provided the copyright notice and permission notice are preserved. That matters if you intend to fork the rule data and ship it inside your own product. Nothing in the README or the repository layout suggests a separate licence for the data directory, but the data files are part of the same repository and the same LICENSE file is the only one at the top level. If your use depends on the data being separately licensed, read the LICENSE file and the docs rather than assuming. This is not legal advice.

Editorial conclusion

Adopt WindowsSpyBlocker if you want inspectable, versioned rule sets you can read before applying, and you accept that the newest release is 4.39.0 from 2022-05-16. Do not adopt it if you need a background service that reacts to new telemetry endpoints as they appear; this project regenerates rules from capture sessions, and the README describes no daemon. Before applying anything, open the data directory, read the rule files for the mode you intend to use, check the docs page for the current collection procedure, and confirm which Windows build your rules were derived from.

Frequently asked questions

Official sources

1. crazy-max/WindowsSpyBlocker on GitHub
2. License: MIT
3. Project website
4. README
5. Releases