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Location tracking of phones is out of control. Here’s how to fight back.
(arstechnica.com)
This is a most excellent place for technology news and articles.
This video, where Veritaseum hacks LinusTechTips' phone, gives a good overview of how it's possible to track cellphones or hack sms, even without asking a carrier or having physical access to the device: https://m.youtube.com/watch?v=wVyu7NB7W6Y
TLDW: cellphone networks rely on old, unsecure infrastructure
I was talking specifically about how telcos behave within law and corp policy.
But yeah a threat actor with money can do anything if they really care.