The lure of "Flash BTC" software often targets people looking to perform "flash flips" or "sending fake BTC." The promise is that you can download this "Core Network 63.0" and send Bitcoin that stays in a victim's wallet for a few hours before disappearing.
In legitimate cryptocurrency network architecture, a "flash transaction" does not exist.
Check out our guide on Cold Storage and Multi-Sig Security to keep your assets safe from hackers.