Cafe Latte attack steals data from Wi-Fi PCs

If you use a secure wireless network, hackers may be able to steal data from your computer in the time it takes to have a cup of coffee.

At the Toorcon hacking conference in San Diego this coming weekend, security researcher Vivek Ramachandran, will demonstrate a technique he's developed to attack laptops that use the WEP (Wired Equivalent Privacy) encryption system to log on to secure wireless networks.

Developed in the late 1990s, WEP was the default method of securing Wi-Fi networks. Though the WPA (Wi-Fi Protected Access) system replaced it, about 41 percent of businesses continue to use WEP. That percentage is even higher among home users, security experts say.

That's unfortunate because WEP has been riddled with security problems. In fact, WEP was blamed for the recent TJX Companies Inc. data breach in which thieves were able to access 45 million credit- and debit-card numbers.

To date, however, researchers have tended to focus on exploiting WEP flaws in order to break into wireless networks. That generally meant that the attacker would roll up near the WEP-encrypted router, crack the WEP key used to encrypt network traffic and then log on to the network.

Ramachandran, a senior wireless security researcher with AirTight Networks Inc., has taken a look at the client side of things and developed a way of tricking a WEP-enabled client into thinking that it is logging on to a network that it already knows.

His technique, which he calls the Cafe Latte attack, allows an attacker to circumvent firewall protection and attack the laptop or to set up a "man-in-the-middle" attack and snoop on the victim's online activity. "Until now, the conventional belief was that in order to crack WEP, the attacker had to show up at the parking lot," he said. "With the discovery of our attack, every employee of an organization is the target of an attack."

There are several steps to Cafe Latte, all of which exploit known flaws in the WEP architecture. First, the attacker programs a laptop computer to act like a malicious wireless network, setting up shop in an Internet cafe or an airport. The malicious PC then begins communicating with other Wi-Fi laptops in range, figuring out the name of the WEP-enabled routers that these laptops are programmed to look for and then cracks the keystream encryption code required to send messages to the victim's laptop.

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