At our office we have bad reception for 3G. We bought a Femtocell device that pr

Question

At our office we have bad reception for 3G. We bought a Femtocell device that provides a 3G connection for one specific mobile provider. This device is connected to our network via ethernet. I cannot use this device at our office, because I use another provider.

Thinking about this - it could be that I use connections like this without knowing it. Take imaginary John, living in an area where connection is bad. He has bought and installed his own Femtocell at home. Not only he connects to this device, but everybody in range of this device - not?

When my direct connection to my provider fails, and I'm in range of John's home femtocell, my SMS, phone conversations and internet data are transferred over his home network.

1. Is this traffic encrypted and safe?
2. Is it true that anybody can connect to this device and use bandwidth?
3. When a phone connects to this femtocell, does it have access to the local LAN?

Explanation / Answer

According to wikipedia's article on Femtocells, you have to manually authorize what phone is able to connect to the network (and there is an upper limit), and these phones have to be on the same mobile provider as the femtocell's.

So if John wants to spy on you, he has to authorize your phone and you have to be on the same provider. He also has to act as MitM and break the encryption, or install a rogue femtocell (you definitively have really interesting information on your phone if it comes to that).

From what i've read here and there, no, you don't have access to local LAN, everything is encapsulated with their telecom specific protocols, so you do go through the local LAN but you can't see it. It's as transparent as using a regular cell tower, except coverage.

Now if John works for the NSA, he probably uses a fake femtocell, and you'r screwed.

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