The Wall of Sheep has always been an amusing feature of the DefCon conference. In a very in- your-face way, the project promotes user awareness by scarfing up and exposing poorly secured user credentials as they pass through the DefCon network.

The exposed credentials are displayed (partially obfuscated) on a large screen for all to see. The exposure usually provides for some good laughs at the websites and services conference attendees are using. There's also a fair share of public humiliation for those who are unlucky enough to show up on the screen.

This year, the Wall of Sheep expanded its awareness campaign to mobile device users and the potential dangers surrounding free charging stations. The new awareness efforts are timely as charging stations are being seen more and more in places like airports and conference centers. And who is to say whether or not the charging station is doing more than just providing "juice" to your phone?

I have to say that I really like the idea of the "juice jacking" attack. It's clever, could be designed to be incredibly inconspicuous, and would easily dupe the average business traveler.

If you've not seen one of the charging stations, keep an eye out next time you're at an airport. The basic model includes a female USB port that you plug your charging cable into for power while some of the more advanced models include several different connector types. They typically support iPhones, iPods, iPads, and phones with micro USB, mini USB, and other power adapters.

The obvious issue is that the same cable used for charging can also be used for syncing the data on the smartphone, media player, or tablet. A creative attacker could modify a charging station to steal the data as users plug their devices in for charging. Or, they could build their own, like the Wall of Sheep folks, and deploy it somewhere to slurp victims' phones.

In addition to the data-stealing attacks, there is the possibility of mobile malware being spread to plugged-in devices. For example, if there is electronics and storage capabilities on the charging kiosk's side, an advanced attack could target vulnerabilities in the embedded hardware. A successful exploit could allow an attacker to upload their own code to start infecting all devices as they are being charged.

There are endless possibilities for variations on this attack from creating your own fake charging kiosk to modifying existing ones to steal users' data. It's really not much different from the ATM-skimming attacks that put a fake card reader and number pad over the original one to steal data as it is being entered. Users need to be aware of the dangers and take precautions like carrying charging cables and never plugging devices containing personal and company data into systems they don't own or understand.

I wonder how long before someone identifies an attack like this in the wild, because if it hasn't been done, the idea is out there, and it likely won't be long.

For more information on the Wall of Sheep's charging kiosk awareness efforts at DefCon, Brian Krebs has a great piece with more details here.

John Sawyer is a Senior Security Analyst with InGuardians. The views and opinions expressed in this blog are his own and do not represent the views and opinions of his employer. He can be reached at [email protected]