Hackers Turn Verizon Box into Spy Tool

Researchers at iSec hacked into a Verizon network extender, which anyone can buy online, and turned it into a cell phone tower small enough to fit inside a backpack capable of capturing and intercepting all calls, text messages and data sent by mobile devices within range...

"The level of technical skill that you need to break into one of these, people are learning college. 

A malicious person could put one of these, with a battery, in a backpack, and go downtown - to a place like Times Square or Wall Street...

Frankly, these devices scare us. It is not the NSA tapping ordinary people. It is about ordinary people attacking ordinary people." (more)

Note: Verizon says they fixed this particular issue.

Warning: Femtocells in general, however, offer a new playground to hackers and criminals alike. Cut back on your confidential transmissions in densely populated areas.