Wednesday, July 01, 2009

Strange Cellphone Behavior

Hey all,

I know this blog post is a bit weird, but I reckon I'd share this: For some reason that is quite unknown to me, my cellphones have a habit of developing strange behaviors. I used to use a Nokia N73, which developed the following habit:

When in foreign time zones (Japan, Norway, USA) the phone would send more-or-less random old text messages to more-or-less random people from my address book. There would be a merry mix & match between the two, leading to more than one amusing misunderstanding that needed clearing up.

Then, at some point last fall, I switched to the silly shiny Apple telephony device (perhaps people do better QA on their backdoors on that platform). For a few months, the problems went away.
This changed last week -- now, when I send text messages to certain numbers, the phone seems to send a more-or-less random old text messages that has already been sent to the same number along with the message. This is a bit nicer (as it will not mix & match), but still annoying.

So .. uhm ... I am trying to come up with plausible explanations for this behavior. Can anyone offer one ? My total-guess-in-the-dark ideas would be:
  1. Current behavior is caused by international text message routing weirdness -- e.g. text messages I sent a few days ago in the US get duplicated for some reason and re-sent
  2. Both current and N73 behavior is triggered by shoddy QA on lawful intercept systems
  3. Both current and N73 behavior is triggered by shoddy QA on the side of the parties that backdoor my phones
Now, I don't know if anyone else has ever suffered from this, or if there is a perfectly valid and proper explanation, or if there is an easy way to do diagnostics, but:
  1. If you backdoor my phone, fix your software. Kthx.
  2. If you write LI software, fix your software. Kthx.
  3. If there are multiple people backdooring my phone, please test for interoperability between your tools.
So, any other theories on what might be going on ?


Unknown said...

timezone mixup? Maybe the phone thinks it has not sent certain SMS yet, and, therefore, sends them out when you send a new sms.

jz said...

well, your phone's been haunted? :P

how about this : is your phone service using satelites? signal status is not good at some points in some country. your phone communicates with relay bases, and this base tries communicating with the satelite(or another base), but CRC checksum continuously doesn't match. the base tells the satelite(or another base) that re-send is required, but this message also gets corrupted and the satelite(or another base) re-sends the message which was sent last time.(supposing it's still in the log).

Michael said...

I'm not sure if you switched carriers...if not it's possible your account is jacked. If you send a text to someone and their phone is off, the phone will get it when it's turned on. My assumption is that there is some sort of queuing system for outgoing texts that sit somewhere on the carrier's end (similar information is used for tracking to charge you for your texting overages). Is it possible that whatever this mechanism is on their end is what's hosing your account? I figure the reason you saw the issue go away for a while after switching to the iPhone is that your account had to be modified to take advantage of the new phone, thus temporarily clearing up your problem.

It's about the only thing I can come up with.

CG said...

i'm gonna go with #2

Unknown said...

Halvar, have you tried ruling out any SIM cards or otherwise (not sure if you even have one.) but in the past I've had issues with faulty or failing SIMs doing all sorts of weird things to my phones....

Unknown said...

Try switching operators (carriers). Backdooring the phone is much easier when one knows certain magic keys global to the network. No exploits required.

Unknown said...


i would not think that there is the need to hijack your phone to intercept text messages, as they are plain text in the ss7 network anyway.
But the fact that the problem went away when changing to another phone is a bit suspcicous. Did you change your number ? Even if not, then the following would apply: Changing to the iphone requires a new HLR profile, hence the information to reroute the SMSC to the LI number might have been overwritten so that would needed to be fixed after some time.

A more resonable explanation could be that either the LI is buggy, or the routing on SCCP layer is buggy, means your MNO LI SMSC does not get the forwardSMack, hence it times out and resends. But why would that happen when triggered by a new SM ? fishy fishy

see also

Which explains the stuff quite well.