This is an interesting facet of the coronavirus pandemic and I am exploring this topic in detail. I’d put up a future blog post to explain the rationale of privacy/security and anonymity and suggest ways and means to limit the data collection on individuals.
Do read this up for a simplified explanation of what’s really going on.
If you are not familiar with contact tracing, I suggest you first read this blog post that explains the topic and the various methodologies that are being used and developed globally.
At a high level, the way this technology works is by having an app on your phone broadcast a random, unique identifier over the device bluetooth antenna, and simultaneously listen for other phones broadcasting their identifiers.
Your phone keeps a log of everyone you come into contact with who is running this app and is broadcasting advertisements over the Bluetooth service. It is important to note, Bluetooth is not the same as GPS, it cannot determine your physical location. Your contact list is simply a giant list of random numbers representing other devices that were near you at some point.