This is one of my favorite things about Android. It's trivial to restrict access using AFWall+ . You can block all access, mobile data access, WiFi access, it any combination thereof on a per app basis. Highly recommend it.

Unfortunately requires root though, which means for the vast majority of Android users this is not an option.

Yes very true. I've been rooting for years so don't usually think about that, but yes you have to be rooted. It's sad that for proper security you have to root your device. I'd love if they built that firewall into Android.

Anticipating a question, the best phones IMHO for rooting are the OnePlus phones and Pixel. Motorola had been good in the past but you have to get a code to unlock the bootloader (which I don't like).

NoRootFirewall is much the same. If you can install LineageOS it lets you revoke fine grained permissions without the app knowing.

Plus, regardless of background or technical expertise, rooting your phone dramatically decreases security.

Downvoters: so what security features do you lose and gain when you root your phone? You've weighed the pros and cons, right?

Not a down voter, but I disagree with you.

There's a fantastic example in my sibling post. Rooting gains you the ability to more tightly control network access. That alone is massive for privacy and security.

Obviously you have to run code with lots of permissions, which means you could be highly compromised by a malicious app. The onus on the user is much higher to vet apps. At the end of the day you have to place some trust, even if you don't root. It's a game of balancing tradeoffs.

It's overly simplistic to say that rooting dramatically decreases security regardless of background or technical expertise.

Thanks for answering. I guess now that it's possible to install your own key to verify rooted images in many phones, the problem is somewhat attenuated. Losing verified boot is a major loss.

So yes, that was a bit overly simplistic. I rooted my phones for a number of years before carefully looking at the pros and cons and deciding it was a poor choice for a consumer mobile phone. Obviously, we need root access for our dev machines and servers. But I try to follow the principle of least privilege, and in that case, not clear why root would be needed for a mobile phone.

But I concede that for some use cases, it can be a trade-off.

What other security advantage of rooting can you name besides tighter control of network access? Also, note that there are a few apps that allow some degree of firewall with unrooted phones. I also suspect there's a lot of room for improvement there.

Maybe I understand you wrongly, but when I open the setting of individual app in iOS, I can revoke both cellular and WiFi access for it.

I’ve found blocking an iPhone on my WiFi AP effectively cuts it off from the net. It may have cell, but I think iOS prioritizes the WiFi connection because it’s live to the AP, even though all requests stop there.

Why not just turn off cellular data?

Honest question: but what’s the threat model for wanting an OS to block this? I’ve so far only thought of leaking IP address and Bitcoin mining. But any website already easily has both capabilities (with somewhat arbitrary open sockets after the WebSockets handshake). Is the expectation that an app implementation should have less permissions than an equivalent website and so be the “safer” option?

I want to ensure that the app is just locally computing the decibel level, rather than streaming out data about what it's hearing.

I would ideally want websites to also have a "no more network access after your initial load" mode, but as you say that's fundamentally incompatible with modern web development. So I kinda just accept the loss there.

Isn’t it the same as any other access permission ?

For instance is there any specific model behind blocking device location, short of just not wanting to share the info ?

I’d see not wanting an app to send anything related to your device nor that it was even opened to be of the same kind.

Stock Android is the same, but MIUI (Xiaomi skinned Android) does allow you to control which apps have internet access, and whether they can use mobile or wifi networks.

You can turn off WiFi and then revoke cellular data for a specific app. Not the same thing but still effective, especially if you are only going to use an app once.