How to Block Private Network (Intranet) Access Globally in Google Chrome

The Intranet Exploit Vector

Google Chrome supports an advanced architecture known as Private Network Access. By default, if you are browsing a public website on the internet, that website can execute background JavaScript to silently probe devices on your private, local home network (your Intranet). Malicious websites use this tactic to scan for vulnerable routers, smart home appliances, or unsecured NAS drives located on your 192.168.x.x subnet. The website can then attempt to exploit these local devices directly from your browser. To secure your internal home network against external web scripts, you must paralyze this API.

How to Block Private Network Access Globally

You can permanently sever the browser’s ability to bridge the public internet with your private network via Chrome’s Site Settings.

1. Open the Google Chrome desktop browser.
2. Click the three vertical dots (⋮) in the top right corner and select Settings.
3. In the left-hand sidebar, click on Privacy and security.
4. In the main window, click on Site settings.
5. Scroll down to the “Permissions” heading and click to expand Additional permissions.
6. Click on Private network devices.
7. Under the “Default behavior” heading, select the radio button for “Don’t allow sites to request access to private network devices.”

Total Subnet Isolation

The change takes effect instantly. Google Chrome will completely sever its internal ability to route external requests to your local subnet. The browser is now permanently blind to your router and local hardware. If a public website attempts to execute a script to scan your 192.168.1.1 IP address, the API call will instantly auto-reject in the background, returning a CORS (Cross-Origin Resource Sharing) error. This guarantees absolute isolation, ensuring that public websites can never interact with the secure hardware residing on your private home network.