This talk will consider global reliance on a coded radio signal that was state-of-the-art when it was specified in the 1970s as it becomes trivially spoofable today with battery powered COTS hardware & open-source software. Spoofing GNSS to fool location & timing receivers is nothing new, but how can we engineer the very technology that enables the spoofers to build defences that protect critical infrastructure? Taking existing CyberSecurity methods to identify & classify the threats and suggesting new & novel ways to protect critical timing sources, signals & references for Telecom, Power, Financial & Transport users.