You do it because it makes an attacker’s life harder because now I have to find two bugs instead of one.
The entire boot chain of the phone up to the apps you run are verified successively by the component that loads it. A digital signature helps ensure that only trustworthy code ever runs. A bug must be found to bypass these checks to load malware code. For example, a bug in the image code in a web browser might cause loading of code that isn’t checked. This way the malware gets smuggled onto the phone.
This means that if you get hacked via one bug and malware is loaded, the attacker has to work harder to solve the problem of how do I convince the phone to load it again at boot because the code it’s made of isn’t going to be approved code. When you reboot, you are effectively forcing a validation that all the code you have running is authentic, which would exclude the malware. Trick me once sure, can you survive a full pat down? Probably not. It’ll get caught.
Unless I have a second bug to fool the normal code loading systems too, the malware can’t run. You have to go back and trigger the first bug again somehow, which places more strain on the attacker.
Thanks for taking the time to write that out. I found it really helpful.👍
I love to talk about computer security. I don’t get the chance often enough.
I hope you get more chances to do so; you explained the situation in a much better way than the article and convinced me to reboot my phone.
Exactly, as you already explained in detail this is primarily for security.
GrapheneOS has a feature to set a time after which the phone reboots in case there was no unlock. So in case a bad actor gets your phone they only have that time with a running system after the first unlock. However, if you use it normally, and unlock it in regular intervals it does not auto-reboot. This is especially neat if your threat level is not “investigative journalist” or “political activist on the run”, because then you can set the time to a longer interval and the phone does not reboot every night when you are asleep which also leads to the SIM card being locked and nobody being able to call you…
I remember this feature, and I wish it was a standard Android feature. It sounds like it would be trivial to implement and could be completely optional.
But that only works for untrusted code escaping a sandbox, right? It does not help with malicious code embedded into legitimate seeming apps. The later vector seems easier, especially on Android, no?
I don’t really consider a malicious app to be an exploit. In this case, the software is doing exactly what it was designed to do – malicious activity. It’s not being manipulated to perform unintended operations through the exploitation of a software bug. Code signing and secure boot are not effective in the face of intentionally shipping malicious code to end users. It’s designed to frustrate actual hackers.
For malicious-by-design apps, we rely on a central app store that hopefully reduces the number of bad apps in circulation. If you publish malware, eventually you get caught and we know who you are. Sandboxing with a permissions system helps prevent apps from performing actions contrary to the user’s interests. E.g. why is my flashlight app asking for my contacts when I pressed ‘change color?’
If you directly exploit your way in, it’s harder to know who did this and why because you didn’t go through any central vetting or accountability system, and you’re not so easily bound by the permissions system. It depends on what your bad guy’s goals are, what they want, whom they’re targeting. Force your way in the back entrance, crawl through an open window (like a weak security setting), or lie your way in the front door (trojan)? It depends.
None of it is perfect, but I’m sure OS design experts would love to hear about better solutions if any exist.
wouldn’t a malicious app still be an exploit though? I’d say that if I download an app for playing a game, but instead it was designed to also upload my private photos to the attacker’s server, i’d say that’s still exploiting. It’s just exploiting my expectations of what the app should do, rather than leveraging a system weakness (which it probably does, anyway)
Pixels with grapheneos can reboot automatically after a number of hours with the screen off (unattended because you are sleeping). But this would also interfere with Whatsapp backup, which happens overnight.
Nope! From Kaspersky:
Reboot Daily: According to research from Amnesty International and Citizen Lab, Pegasus often relies on zero-click 0-days with no persistence. Regular daily reboots can help clean the device, making it necessary for attackers to repeatedly reinfect, thereby increasing the chances of detection over time.
For a case with persistence, Lookout notes another bug was required and details the extra work.
Idk man I just do it when my phone won’t ring when I get a call from my dad or doctor or something, so I have to go delete the voicemail and call them back. So like, every couple of weeks. I think it’s a Samsung thing, happened on my last phone too.
Nothing wrong with that. I don’t think it’s a mistake to not reboot your phone until you need to. It’s your phone. It’s not like rebooting your phone will save lives or the planet.
My wife doesn’t even use a lock screen password. I’m interested in the nuances of such things.
Jokes on them, my S22 Ultra restarts in it’s own. Even when I don’t want it to.
Sounds like my wife’s old Samsung phone as well… I’m sensing a common theme…
Don’t e.g. alarm apps not work after that until you unlock your phone since the device data decryption keys weren’t kept in RAM after rebooting? I have that feature off since I don’t want that to happen. Afaik AOSP has added that to make installing updates more seamless, but it’d be useful for this too. (And since Samsung usually sucks at improving their already self-made stuff to align with AOSP, like Virtual A/B updates, I’m just assuming this)
Really? My S22u is super stable. I don’t think it’s ever crashed. The current up time is 377 hours. But that’s only because of the 6.1 update a few weeks ago.
Replace your battery.
Your phone is 2 years old.
Phone batteries are typically designed to last around 2 years before they really degrade because a lot of people buy new ones around every 2-3 years.
When the battery can’t sustain the same throughput, the phone can handle this in one of two ways.
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Slow the phone down. This is what Apple does and why people with iPhones 2 years old complain the new update slowed their phone down.
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Don’t slow it down but if the throughput drops below what’s needed, die and reboot. This is what your phone is doing.
Getting a new battery will probably stop this behavior (and for iPhone users reading this, getting a new battery for a 2 year old phone will make your phone faster).
Edit: Seems some of you don’t believe me looking at the downvotes. Look at number 8 in this list: https://helpdeskgeek.com/help-desk/why-your-android-phone-keeps-restarting-and-9-ways-to-fix/
I have an s22 ultra as well, and it’s fine? Sounds more like they have some rogue apps causing the restart.
TL;DR:
Restarting your phone once a week can help improve performance and security.
- this is the same for routers and it’s commonly known as a power refresh
well, I mean… anything can leak memory. but yeah, enterprise/carrier grade devices are designed to be in continuous use for years and they generally do that pretty well.
Even then, some places will reboot on a schedule when nobody should be using it.
I have some entry level “enterprise” hardware (Mikrotik router and Ubiquiti access point) and I auto-reboot mine weekly. In addition to maintaining performance and minor security wins, it also helps ensure everything csn survive a reboot (e.g. all configurations have persisted to disk).
It’s good practice. Some people brag about continuous uptime, I see it as a liability.
Feels like I need to reboot my iPhone daily in order to keep applications and tabs from being terminated from out of memory issues as quickly.
Yes, a reboot is a reboot. As long as the boot sequence cycles through where the code is validated, you’re good.
a reboot is a reboot
Not always. Some phones will do a sort of “soft” reboot, which doesn’t actually go through the entire boot process, but is more like logging out of the active OS user and back in, reloading some of the OS but not all.
Pretty sure a system update would trigger a full reboot, though, but I’ve seen the option for this sort of partial reboot in the power menu on some devices in the past.
GrapheneOS has a convenient auto-reboot feature
TIL, I use GOS and never thought to look, I just see a banner saying there’s been updates and I’ve got “update and restart now”, “schedule restart” and “I’ll restart myself when ready” (or some such).
The main purpose of this is actually security. Because when the device is in BFU (before first unlock) state, it’s much harder to gain access to the data (without the correct unlock credentials). During the reboot, the encryption keys are wiped from RAM, making it essentially impossible to access the device, since brute-force unlock attempts are prohibited by Weaver API, which is enforced by the Titan M2 hardware security module. You can read more about this at https://grapheneos.org/faq#encryption
I will give that a read. I have been unintentionally using this feature, anytime I expect I won’t use the GOS pixel for a bit I restart it, I’ve also found it disables biometrics as a security measure. Cool stuff.
Samsung has had the auto reboot feature for a long time too.
“you do need to restart your phone regularly to rid it of demons”
typo: “daemons”, not “demons”.
