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Hardware Hacking Security Linux Build

AT&T Microcell Disassembly; Security Flaws Exposed 82

Posted by Unknown Lamer
from the bind-all-the-addresses dept.
CharlyFoxtrot writes "The geeks over on the fail0verflow blog took apart an AT&T Microcell device which is 'essentially a small cell-tower in a box, which shuttles your calls and data back to the AT&T mothership over your home broadband connection.' They soon uncovered some real security issues including a backdoor : 'We believe that this backdoor is NOT meant to be globally accessible. It is probably only intended to be used over the IPSEC tunnel which the picoChip SoC creates. [...] Unfortunately, they set up the wizard to bind on 0.0.0.0, so the backdoor is accessible over the WAN interface.'"
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AT&T Microcell Disassembly; Security Flaws Exposed

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  • Re:Improved Roaming (Score:5, Informative)

    by tcampb01 (101714) on Wednesday April 04, 2012 @12:59PM (#39574131)

    It' does have a GPS, but it's not for E911.... you could register the location if that were all it was.

    They won't allow the device to use unlicensed spectrum. Since the frequencies that a company has licensed will vary from place to place, they want the device to know where it's located. It can then determine which frequencies it is licensed to use in that particular area. You'd think a reverse-IP location would be adequate, but the FCC apparently "requires" that they do this with GPS. I had read stories that some customers were allowed to request a bypass (AT&T would remotely program the device location and tell it to ignore the GPS and work anyway) but the FCC forced them to put an end to that practice (the FCC is always so "helpful" like that. )

    There are more ironies... not only does the device need to be near a window where it can pick up a GPS lock, it also tests the signal strength of the standard AT&T towers. It dials it's own signal strength back IF it thinks that the outside signal strength should be good enough. And since the device now has to be located in a window, it'll get better signal than you could realistically get inside your home. And of course being at a window, you cannot locate the device in a central location to offer coverage to most of the home. The result is that this makes the micro-cell transmit the weakest possible signal (and of course you bought it SPECIFICALLY to overcome the problem of weak signals) and if you're not relatively close, the device is worthless.

    It gets worse. AT&T allows a hand-off of a call from micro-cell to regular towers, but it can't do a hand-off in the other direction. And since towers vary their signal strength regularly and the micro-cell is now using it's wimpiest transmit power, it takes very little to make the phone think that it needs to switch to an outside tower. The result is that if you get an outside tower boost from... say 1 bar to maybe 3 bars, your phone will switch to the outside tower. A few moments later the outside tower drops back to it's more typical 1 bar signal strength. Since the call cannot do a hand-off back to the micro-cell... the call just drops.

    After months of frustration, I discovered the solution. There's an external antenna jack on the back. If you ask AT&T about it, they can't tell you anything about it. They don't sell any accessories or even know what sort of antenna would work with this. You can get an external GPS antenna with a long cord (I bought one with a 25' cord.) This allows you to get the micro-cell away from the window and closer to the center of the house. BUT.. the micro-cell also varies its own transmit power based on whether it's able to detect much outdoor AT&T signal. It's in your best interest to make sure the micro-cell gets the weakest signal you can manage. I located my micro-cell to my basement... in a small closet under the stairs. The GPS antenna is in a basement window. Now the micro-cell still gets the GPS lock, but it doesn't get any outside AT&T signal... consequently it's actually willing to put out a much stronger signal and it works all around the house.

    You won't be able to buy the antenna from AT&T. You'll need do a search for a GPS antenna that works with the AT&T micro-cell. I found one via Amazon for $30... one of the best $30 I ever spent. Now the device actually works as intended.

Never try to teach a pig to sing. It wastes your time and annoys the pig. -- Lazarus Long, "Time Enough for Love"

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