SMS is not at all secure. My first out-of-uni programming job was working on SMS value-add services for mobile networks (mostly anti-spam, anti-fraud, anti-spoo

SMS is not at all secure. My first out-of-uni programming job was working on SMS value-add services for mobile networks (mostly anti-spam, anti-fraud, anti-spoofing type stuff and roam steering, but also parental controls and other stuff). It was crazy what weird things we could bend the network to. Obviously, our services ran on the network itself, so had more access than a typical end user, but the protocols have zero built in security, everything on the network was totally open, spoofing is trivial (we could detect much of it with our software, but definitely not all -- mostly all we could do was consistency checks, but if you carefully crafted a fake packet, there's nothing we could do). As others have stated, the over-the-air encryption is often.. not good.. so getting access SMS like we had seems very possible. And since its not end-to-end encrypted, a bad actor within the network could also trivially access messages (we could! we even intercepted some of our own messages for testing, it would have been a simple regex to read other people's messages). This was ~15 years ago, but I doubt much has changed.