[EAS] Decoding cell broadcast diagnostics on your iPhone

[Sean Donelan]

On your iPhone (and android, and likely other cell phone OS), there are 
detailed diagnostics logs. On your iPhone, look under

Settings->Privacy->Analytics->Analytics Data->awdd-<date ...>

"awdd" means Apple Wireless Diagnostic Data.  In the file for October 3, 
there may be something that looks like this:

metriclogs {
  triggerTime: 1538590702067
  triggerId: 524356
  profileId: 174
  commCenterGSMCellBroadcastEvent {
   timestamp: 1538590702066
   message_id: 4370
   message_code: 0
   update_number: 0
   emergency_user_alert: false
  }
}

Its usually a big file, so you'll need to scroll a long way. The entries 
are in triggerTime order, which is the date/time, will help narrow down 
where in the file.

That is the diagnostic data about the WEA Presidential Alert cell 
broadcast message. The message_id 4370 is the GSM code for CMAS Alert 
type Presidential. An Amber alert is code 4379 and other codes exist for 
other messages.

The trigger time is local time in milliseconds. That means my phone got 
the cell broadcast at Wed Oct 03 2018 14:18:22, and displayed/alerted 
on the phone 1 millisecond later.

On my iPhone, I can also see in the awdd log I was on a voice call which 
ended about 10 minutes before the cell broadcast. The awdd shows I lost 
cellular reception when I got on the metro subway later in the day, and 
the times I regained cellular reception. The awdd log also shows when my 
phone was roaming on other carriers, using LTE or 3G or wifi.

An version of the diagnostic data log is uploaded to Apple periodically 
depending on your privacy settings on the phone. I believe the uploaded 
data is anonymized, and certain details omitted, but I don't have first 
hand knowledge of what data Apple actually gets.  Individual apps also 
upload data to the app creators.

In theory, Apple and other cell phone manufacturers with handset 
diagnostic data could create a nationwide report based on the data they 
collect.