[rl3]

The Snowden leaks confirmed NSA has the ability to conduct co-traveler inference.[0] In other words: finding mobile devices proximate to a targeted mobile device, based on similar vectors. Perhaps even making associations in absence of targeting via patterns in device proximity over time.

It probably gets real interesting when they're trying to distinguish between various modes of transit, such as a city bus, an Uber/Lyft/taxi, and a private vehicle not participating in rideshares. Of those examples, the latter would suggest the highest degree of association.

Pure speculation, but I wouldn't doubt they take a peek at ridesharing data for co-traveler inference purposes. Knowing if a rideshare driver is on or off the clock would be incredibly valuable information in that context.

[0] https://www.washingtonpost.com/apps/g/page/world/how-the-nsa...

[jandrewrogers]

Graph reconstruction from space-time event data goes far beyond the above in terms of capability. You can infer relationships between people that never co-travel, infer that people have been places that are not in the event data, etc by stitching together large numbers of orthogonal event streams over long periods of time. It is straightforward to distinguish between various modes of transit analytically. The "metadata" that simply indicates an event in space-time is far more valuable analytically than the data because it is possible to reconstruct so much with it that isn't contained within the data per se.

I was doing all of this five years ago, the capability has been around for a while.

[pjc50]

Do you ever worry that this data might be used for bad purposes?