A fake CAPTCHA or error page pressures you into copying a "verification command" and running it on your own computer. It's a scam — that command quietly hijacks your machine. ExecFence catches the trap and warns you first.
Every step below is normal on its own. That's why antivirus misses it. ExecFence watches the one place the chain goes wrong.
A page shows a CAPTCHA, a "security check," or a broken-page error.
It hands you a "verification command" and pressures you to run it yourself, outside the browser.
The command it put on your clipboard quietly downloads and runs someone else's program.
The instant those combine, ExecFence warns you in plain words — before anything runs.
Silent on the pages developers really copy commands from — GitHub, Homebrew, package managers. It only speaks up when a page is trying to fool you.
Every warning tells you what the page asked and what the command would actually do — reach the internet? download a program? run it? — in plain English.
Everything is checked on your own computer. It never reads your system clipboard and never uploads what you copy. One permission, no browsing history.
Clear the tricked clipboard, close the tab, inspect the command, or continue anyway. ExecFence warns — it never locks you out.
Install ExecFence (developer mode — no store needed), then open the safe demo. It's a harmless copy of a real scam page: the moment you copy the command, ExecFence throws the warning. Everything on it is inert and points only at addresses that don't exist.