Genuinely curious, does the telephone system have enough scope to make it dangerous?

Elevators are extremely hackable all over the world. It’s generally not considered a problem because it requires physical access, specific knowledge, and defeating cameras to exploit successfully.

What can you do with the telephone system?

Some physical constraints do not allow for the best security, and those physical constraints will always win out in the real world. When presented with the pick two of three options of fast, cheap, secure/done right, fast and cheap will always win out.

The “new” phone system (SS7) still relies on implicit trust and a lack of security.