So, a bunch of SIM card keys were most likely stolen, but Gemalto claims that this would only affect 2G networks.

Supposing all that is true, it's still the case that 2G networks exist alongside the 3G and later networks. Is that enough to effect an intercept?

Would it be possible then to cause connections 3G or later networks to fail, so that devices would fall back on the compromised 2G network?

What specifications would I need to be familiar with to understand this stuff?

  • 2
    It's definitely possible. Jam the 3G frequencies and the phone will fail over to your (compromised) 2G network.
    – user42178
    May 5, 2015 at 6:53
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    I figured that would be possible. Jamming the frequencies is fairly crude though, and untargetted. It would affect all people in the area, and be too easily noticed to be much use for the spooks unless they were really desperate. I'm wondering though if there might be more subtle effects that could for example obstruct the connection of a targeted device. By analogy, you can disrupt SSL without hacking the crypto, by just messing with the TCP layer's handshake.
    – mc0e
    May 5, 2015 at 7:42

1 Answer 1


Yes it's possible. Not sure if you know how IMSI catchers operates.

An IMSI catcher blocks the smarter 3G and 4G signals, forcing mobile phones in the area to switch to the unsecured 2G service — something that phones also do routinely in more rural areas, where 2G service is widespread.

The IMSI catcher then poses as a tower and "catches" signals.

The IMSI catchers take advantage of a vulnerability built into the system. Phones using 3G or 4G technology can authenticate cell towers, but phones on older 2G systems cannot tell between real and fake towers.

IMSI catchers hijack the phone's signal and intercept the contents of calls and texts.

The government agencies and law enforcement can use these, but you can always buy one on the black market or build one yourself.

You can find a lot of information on the internet about IMSI catchers

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