Received SMS message via SIM# while Airplane Mode is active

Fog-Nearby

Hello all,

Pixel 8 running GOS v2024091900 Stable.
I just received a spam SMS message via the default Messaging app to the phone number associated with the SIM in my phone. I keep Airplane Mode enabled at all times, hence my post here hoping for some help on how this might have happened and if my settings need to be adjusted.

Under Settings > Network & internet, Airplane mode toggle is On.
Under Settings > Network & internet > Calls & SMS, Wi-Fi calling is Off. The Calls and SMS options above Wi-Fi calling are both grayed out.
Settings > Network & internet > SIMs is grayed out.
I have no eSIM(s).

I’ve never setup WiFi calling with this carrier. In fact, I never use this SIM… It is a super cheap US Mobile plan I keep for emergencies only when I don’t have a strong data connection for Signal/VOIP.

If anyone has advice on settings I still need to adjust beyond the above, I’d appreciate the help. My goal is to have the SIM’s cellular communication disabled entirely and only available when I toggle off Airplane mode.

Probably9857

Fog-Nearby My goal is to have the SIM’s cellular communication disabled entirely and only available when I toggle off Airplane mode.

That is exactly what Airplane mode is supposed to do. No other settings changes should be required.

I don't have any explanations, but I'll be interested to hear what more knowledgable people have to say.

zzz

Fog-Nearby My goal is to have the SIM’s cellular communication disabled entirely and only available when I toggle off Airplane mode.

cellular communication

Technically you should already have disabled cellular communication with Airplane mode.
According to the official GOS documentation:

Activating airplane mode will fully disable the cellular radio transmit and receive capabilities, which will prevent your phone from being reached from the cellular network and stop your carrier (and anyone impersonating them to you) from tracking the device via the cellular radio.
https://grapheneos.org/faq#cellular-tracking

Perhaps the technicality here is that you're still receiving SMS data via WiFi radio / WiFi network, rather than cellular radio / cellular network?

If anyone has advice on settings I still need to adjust beyond the above, I’d appreciate the help.

Try revoking the SMS permission from the default Messenger app?

Further testing and knowledge would be required to tell if:

A. revoking this permission actually rejects incoming SMS messages (?),
or
B. if the messages are still stored on the phone on some deeper system level, but just never exposed to any app (?)

Ultimately I'm also not sure and would be interested to learn more.

flighty_sloth

Fog-Nearby I suggest check the following setting:

Settings . Network & Internet . SIMS . (YOUR SIM HERE) . Wi-Fi Calling

Be sure it's set to OFF or you may still receive calls or sms on WiFi with airplane mode enabled.

Also worth noting: This setting bypass your VPN to connect directly over the internet to your carriers servers.

Fog-Nearby

Only a few seconds after posting this, I received a second SMS from a different number but the same message about a Western Union verification code.
I don’t use Western Union. I assume someone is trying to get into their account and either had my SIM# in the past or are fat fingering it.

Fog-Nearby

Found this thread that seems to be related although no definitive root cause:
https://discuss.grapheneos.org/d/3564-why-does-sms-still-work-in-airplane-mode

I was connected to Wi-Fi when these SMS messages came through. I have never turned Wi-Fi calling on. I gathered from the thread above that SMS messages to your SIM# may still be received (perhaps carrier-dependent), even when Airplane mode is enabled and Wi-Fi calling is off, so long as the phone is connected to Wi-Fi?

Eagle_Owl

Fog-Nearby
Hi,
It is certainly not an attempted attack or a bug in GOS if an SMS reaches you in flight mode.
This is a feature that more and more network operators are offering.
And this feature is desired by many customers who are in places where they are in a dead zone but can use a WLAN.
This allows you to send/receive text messages and make calls (WiFi calling) via WiFi in a dead zone.

(I hope, DeepL has translated it correct: Dead zone – I mean regions without cellular reception)

de0u

Eagle_Owl (I hope, DeepL has translated it correct: Dead zone – I mean regions without cellular reception)

Yes, that's fine.

Fog-Nearby

Thanks, all, for the replies.

zzz Technically you should already have disabled cellular communication with Airplane mode.
According to the official GOS documentation:

Activating airplane mode will fully disable the cellular radio transmit and receive capabilities, which will prevent your phone from being reached from the cellular network and stop your carrier (and anyone impersonating them to you) from tracking the device via the cellular radio.
https://grapheneos.org/faq#cellular-tracking

Perhaps the technicality here is that you're still receiving SMS data via WiFi radio / WiFi network, rather than cellular radio / cellular network?

I’m inclined to agree. I trust GOS/Airplane mode enough and the above doc is what helped me decide to leave the SIM in the phone w Airplane mode enabled.

What I did not realize is that SMS messages can still be received by the SIM phone number in Airplane mode if the phone is connected to Wi-Fi, even when the Wi-Fi calling option is disabled and has never been enabled.

I opted to disable the SIM: I briefly disabled Airplane mode and navigated to Settings > Network & internet > SIMs, toggled off Use this SIM then re-enabled Airplane mode. I no longer receive SMS in Airplane mode when connected to Wi-Fi.