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Security without penalty

Posted on 30 Mar 2009 at 16:17

Paul Ockenden reduces the strain on his netbooks, continues his Wi-Fi investigations, and reveals the perils of using a mobile as a modem.

The real question implied in your email is "can the network tell that I'm connecting my phone to my laptop and using it as a modem?" and so far as I'm aware, the answer to that one is no, it can't - at least not today. It might be able to spot increased overall usage and perhaps peculiar patterns of traffic (say, due to video-streaming protocols that your phone doesn't support natively), but I'm not aware of any network that does this degree of traffic analysis except under exceptional circumstances. That's not to say that systems won't be deployed in the future that are able to detect such usage patterns, but right now I think you'll probably get away with it. Whether you want to continue to risk it isn't something I can tell you, but is a matter for your conscience and your nerves - but frankly, in this scary economic climate, with employers looking for any zero-cost way to reduce headcount, I'd worry more about the job than having my mobile contract terminated.

Ping!

I'm almost too embarrassed to write about this one because it's such a head-slapper (you'll see what I mean when I get to the dénouement). It revolves around a customised alert tone that I use on my BlackBerrys, a version of the standard "Sonar" tone that I've manipulated so that its volume is extremely low: I have a special profile set up called "silent-ish", which deploys this super-quiet ping sound for things such as emails and SMS alerts, so that if I'm sitting really close to the phone I might just hear it, but it's quiet enough that it won't distract any co-workers (and it doesn't annoy the missus quite as much either).

I'd been using this setup for years without a problem, but recently I found that occasionally my phone would emit a loud ringing sound instead of its usual quiet ping, which was most odd. I checked the profile and that was fine, I checked the sound sample and that was fine, and most times it would work as it should - just occasionally I'd get that awful ringing. Then I noticed that the ringing was happening only when I had the BlackBerry tethered to a computer via a USB lead, so my immediate thought was that perhaps this was causing it to switch to the "holstered" settings in the profile - but it wasn't that, because when holstered it was set to vibrate only.

I put up with the problem for several days. Each time it happened I'd check a few more settings, but I couldn't find the answer. Then a few days later, I found myself looking through the BlackBerry options pages for something completely unrelated, and I noticed that I'd previously ticked the option to enable "Mass Storage Mode" whenever the phone is connected via USB, which allows the PC to see the microSD card in the BlackBerry as a removable drive. But while it's doing this it also prevents the BlackBerry operating system from having access to the card, and guess where my low-volume sound sample was stored? Yep, on that memory card. So while tethered, the phone couldn't access the quiet sample and played that default loud ring tone instead. I'd only encountered the problem recently, because on my earlier BlackBerry devices I'd saved the special alert tone to their internal memory, but when swapping between a Bold and a Curve 8900 I'd used this memory card to transfer the sample so that when I set up the tone in the profile it picked it up from there. I now have a sore, hand-shaped red patch on my forehead.