They run a mini Linux distro and you can ssh or tyy into them if you have a serial port. They have access to much of the hardware but usually over something like a serial interface but still can inject code and stuff. They are a completely secret self-contained computer and I don't even think they get updated for security. They could easily be hacked by anyone probably mostly government regimes. There is only a few companies that make them and they are ultra secretive and protective over them. This is the main reason it's nearly impossible to get an open source phone. Arm is proprietary, modems are proprietary. They run blobs. I have probably the one phone in existence that can run an open source modem firmware, and interestingly I have figured out that there is basically no security whatsoever on the cell networks. (Monopolies gonna monopoly) So that might be one reason they are so secretive about it, another reason is because they don't want citizens being able to just have open source radios that they can't easily hack or sell to drug cartels or something.

It does have complete access to your mic and Bluetooth and other stuff since they share buses, it has access to all your data being sent. It can record phone calls. It can triangulate your position. It can even imitate other modems to pick up people's messages and calls, which means not only can it spy on you but also it can spy on other people around you. I don't think it's really possible to disable these things completely outside of physically cutting power. They boot up with the phone and can probably run even when the phone is powered off since it's a self contained system, often with a direct connection to the battery.

Between Bluetooth, and cellular modems, they have basically complete access to many bands around you, as well as sensor data and sound and video, and with satellites recording the entire planet, they can trace anyone who doesn't have a device back in time anyways. Cell towers can triangulate you as well and do. It's part of location services in all phones now. The modems can connect to almost any towers at least for "emergency purposes".

Basically the only place that's safe now is inside your own head but even that's becoming unsafe because of AI that can read your facial expressions and infer your mental state.

The ways they get around the legalities is originally with the eyes programs, where countries would spy on their allies citizens to escape domestic laws like those pesky constitutions, but nowadays they just literally sell everyone's personal data to the highest bidder, international or domestic. The CCP can buy this I do just as easily as Black Rock can, not that Black Rock is or every was an American company. These are international corporations that exist outside of the idea of a state.

It's also not the CIA or NSA spying on you, but private companies. Even the people in the CIA and NSA aren't allowed to know about the extent of the true intelligence apparatus which is completely secret, outside the law, and contained entirely in international corporations. The entire Internet has been saturated with bots since 2001 or something probably. The internet is just a massive psyop and propaganda program. The average person in the 90s would be horrified at the opinions of common people today. Nukes are also probably not real. Just a way to scare people into believing Russia and America and China are actually enemies while they partial up and nationalist culture that doesn't want to give all its resources up to the international secret world management and finance corporation. Fiat currency too is a giant scam to make sure the working person never acquires wealth, and has to work forever, and corporations and wealthy humans who's names will never be spoken publicly, can own anything and have unlimited leverage and I finite money without ever having to work or produce anything of value. The text books in nearly every school in America are made by a company in Israel who was co-founded by glisten Maxwell's father. The left in U.S politics is fake, and the whole social justice warrior movement was a clever psyop to push all the countries further right wing run by internationalist corporations btw. 25% of Americans are addicted to legal amphetamines, more on other drugs like weed which reduces people's ability to understand what's real, Md nearly half of working age people in America cannot or won't find work. Wages have been dropping for decades and now IQs are dropping. Most of human genetics have been completely ruined, as we as humanity has destroyed nearly every honest, principled and empathetic human on the planet for profit.