Security researchers have demonstrated a flaw in femtocells that allows them to be used for eavesdropping on cellphone, email, and internet traffic. The hack was demonstrated on Verizon hardware, and the telco giant has issued an update to patch the vulnerability, but up to 30 other network carriers use systems with software that can be hacked in the same way.

Femtocells are used to boost Wi-Fi and mobile signals within a household, but a common form of software that many devices use has a major security flaw that allows all traffic to be recorded and analyzed. Tom Ritter and Doug DePerry from iSEC Partners demonstrated the snooping hack to Reuters using a Verizon Wireless Network Extender ahead of a lecture at the Black Hat hacking conference to be held later this month.

The researchers bought the Verizon femtocell for $250, and used open source software to test out the bugging attack. They also managed to boost the range of the femtocell to enable a much wider radius of data-slurping beyond the advertised 40 meter radius.

As many as 30 carriers could have hardware at risk, iSEC said, and the attack was simplicity itself – attack code can be pushed to vulnerable devices with no further user interaction needed. Since the firmware of femtocells is seldom updated, an attacker could eavesdrop for some time before being detected, and it's not a hard hack.

"This is not about how the NSA would attack ordinary people. This is about how ordinary people would attack ordinary people," said Ritter.

A hacked device could be placed in locales such as a restaurant frequented by high-value targets, and used to monitor data traffic that comes through the femtocell. The information can be stored and relayed back to the attacker using the adapted device, and used for further infiltration later.

Verizon's update fixes the problem (otherwise, as at past Black Hats, the lawyers would almost certainly have stopped the briefings), but users of their Wireless Network Extender have to be aware of and apply the patch to lock down their femtocells. More worrisome is that the software is used widely in a variety of hardware femtocell systems – all users of all such hardware are advised to seek out their latest firmware upgrade.

"The Verizon Wireless Network Extender remains a very secure and effective solution for our customers," said Verizon spokesman David Samberg in a statement. True – but only if those customers upgrade their firmware. ®