How FNS Shield works.
Written plainly enough for anyone, but with enough technical detail that a security-minded reader can trust it.
The four things it watches for
Every page you visit is checked against four independent detection rules. If any one fires, a full-width warning card appears at the top of the page — you have to see it before you can interact with what’s below.
1. Fake tech-support numbers
Pages that combine a prominent 1-800 number with scare language and unauthorized Microsoft, Apple, or Google branding. Requires the impersonated brand to appear in a heading, title, or logo — not just in prose — to keep precision high.
2. Browser lockers
Pages that force your browser into full-screen, hide the close controls, or spawn dialog loops (“are you sure”, “stay on page”). Real websites do not do this.
3. Remote-access tool downloads
If a page offers AnyDesk, TeamViewer, UltraViewer, Supremo, RustDesk, Ammyy, or Quick Assist from anywhere except the real vendor’s domain, we warn. Scammers typically host these on look-alike domains.
4. ClickFix / paste-into-PowerShell
The newest scam wave. Pages tell you to press Windows+R, open PowerShell, and paste a command. We detect the instruction language and PowerShell syntax markers before flagging.
On top of the four rules, we ship a signed bad-domain blocklist that updates every six hours from our CDN. If the current page’s hostname is on the list, the warning fires before we even run the heuristics.
The warning overlay is un-dismissable by the page
The warning card is rendered into a closed shadow DOM attached to the root of the page. That’s a technical way of saying: the page’s own JavaScript cannot see it, style it, or remove it. Only you can close it, using the buttons we provide. This is important — real scam pages actively try to suppress warnings.
The license lives on your device
When you buy FNS Shield, we email you an Ed25519-signed license key. The extension verifies that key offline against a public key baked into the extension. There are no accounts, no servers to check into, and no phone-home for authentication.
If we ever need to revoke a specific license (refund, chargeback), your extension picks up the change on its next 6-hour refresh via a signed revocation list on our CDN.
What we do not collect
Not collected
The URLs you visit · the content of pages · your search history · usernames or passwords · what websites you go to · anything about your bank, email, or accounts.
What is stored
Your purchase email (to associate your license) · your Square customer ID · which plan you bought · when the license was issued and expires. That’s the whole list. See the Privacy Notice.
It runs alongside your antivirus
FNS Shield is a browser extension. It complements Windows Security, Malwarebytes, Norton, McAfee, or whatever else you already use. It does not compete for the same job — antivirus scans files, we watch web pages. Both matter.
Chrome + Edge, today. Firefox and Safari later.
The extension is Manifest V3 and supports Chrome 120+ and Edge 120+. Firefox and Safari support are planned for a future release. There is no macOS or Windows app to install — it’s pure browser extension.
14-day money-back guarantee. Cancel anytime.