Here is how I've been able to replicate the same "behavior" showed at Atlas "prove" video.
Take a closer look when the balance page starts to show, and "error" appears at the page top, this specific error ONLY triggers when the website could not establish a connection to the HitBTC socket (as anyone can see at the code) So to test it, I've developed this in 30 minutes:
Step 1) Edit computer network hosts and add:
127.0.1.1 st.hitbtc.com
This will prevent the website to find the socket to account info, so the error will appear at the top of the balance page, as we can see here:
Step 2) Install any JS injection like "tampermonkey" and add the script to run at the balance pages:
// Removes the error message (https://imgur.com/ykCViVM)
$("div[class*=styles__alert]").remove()
// Set all balances to zero (as we can see at the video) (https://imgur.com/ggRzH6G)
$("div[class*=main-balance]").html("0");
$("div[class*=styles__cell__cash]:not(:first)").html("0");
// Update BTC and USDT balance (https://imgur.com/ggRzH6G)
$("div[class*=styles__cell__cash]:not(:first)").eq(0).html("1,862.39021193");
$("div[class*=styles__cell__cash]:not(:first)").eq(2).html("5,418,742.84");
So this shows how easily people can be fooled by these scams:
To test propose, you can open the "developer tools" (F12) and paste the JS code into "console" tab to simulate the balance updates (don't need to block the connection, I've done this just to replicate the exact video)