I work as a telecom engineer troubleshooting/programming the Ciena 5164 optical router used for Verizon and At&t. These companies and many of my colleagues know exactly what it was but the more interesting part that raised some eyebrows was the fact that cc payment processing and emergency services/SOS/911 calls WERE possible for most of the affected customers. This is key. (This all runs on the same fiber optic network and should have been ‘down’ also.)
I cannot overstate how anomalous the above fact pattern is because when our networks go down, they don’t go down in this piecemeal way.
Here’s the takeaway: The goal of a ‘cyber weapon’ is maximum disruption. Whoever deployed (tested) this ‘cyber tool’ went to great lengths to pause communication ONLY. This surgeon scalpel approach we saw was a MUCH more difficult task than to just ‘nuke’ the whole system so to speak. A tool like this would need to be tested a few times to ensure a reliable partitioning of the ‘Target’ [calls/data] and the ‘Not Target’ [911/cc processing].
I'm a patriot who loves their country so I will not say what 'it' was/is, but if you reread the above a few times, and ask yourself the right questions, logical deduction should provide the answer.
I got a few theories.
CC processing used satellite or landline comms. Likewise emergency calls can go through any available network. Which would have been T-Mobile. Are most businesses really using cellular networks for their CC processing? Not too long ago I know that satellite links were popular for that application. And there are MVNOs that can operate on multiple carriers. That sounds like a good idea for a high reliability service like CC processing.
GPS disruption. Modern cellular networks require precise time synchronization, which is typically provided by a GPS disciplined oscillator. These oscillators have a holdover specification, a time period for which it can maintain accurate enough time for the system to fully function without a GPS signal. Now, potentially the networks should be designed to operate without such precise synchronization. But in this case the network capacity would be greatly reduced. If that happened, it would make sense to only serve the most important applications.
There was some need to shut stuff down. Such as interrupting NC voting machines. Or reducing RF signal levels for health, to receive a weak signal somewhere, or many other reasons.