They can if given permission to. For certain apps in iOS it’s usually an application asking for location permissions without a real good reason for it, that’s why (in my opinion) it seems like weather apps are some of the worst offenders for this stuff, as it makes sense to give it location permissions. There are other permissions that can be abused as well, but location is the dead give away.
I can’t speak to Android as it’s been a long time, but iOS is pretty strict about what you can and can’t do in the background. There are certain events that will “wake up” an app, even one that is killed. You’re not necessarily safe if you have a bad app installed and kill it. I usually just recommend avoiding free apps that seem super heavy on ads. Because the ad framework is likely abusive, even if the developer didn’t intend it.
Thanks. That's pretty unfortunate. I guess I'll just be event more aggressive about denying permissions requests and uninstalling any app I don't have a good reason to keep now.
I can’t speak to Android as it’s been a long time, but iOS is pretty strict about what you can and can’t do in the background. There are certain events that will “wake up” an app, even one that is killed. You’re not necessarily safe if you have a bad app installed and kill it. I usually just recommend avoiding free apps that seem super heavy on ads. Because the ad framework is likely abusive, even if the developer didn’t intend it.