Hackers can take control of laptops by Wi-Fi, even when the user is not connected to a wireless LAN, according to security researchers.

The hack, which exploits bugs in wireless device drivers, will be demonstrated at the upcoming Black Hat USA 2006 conference during a presentation by David Maynor, a research engineer with Internet Security Systems, and Jon Ellch, a student at the US Naval postgraduate school in Monterey, California.

Device driver hacking is technically challenging, but the field has become more appealing in recent years, thanks in part to new software tools that make it easier for less technically savvy hackers, known as script kiddies, to attack wireless cards, Maynor said in an interview.

The two researchers used an open-source 802.11 hacking tool called Lorcon (Loss of Radio Connectivity) to throw an extremely large number of wireless packets at different wireless cards. Hackers use this technique, called fuzzing, to see if they can cause programs to fail, or perhaps even run unauthorised software when they are bombarded with unexpected data.

Lorcon is the work of Joshua Wright, security architect of Aruba, and author of a previous tool which exposed a Cisco flaw, as well as a mover in IEEE 802.11w Wi-Fi security. Using it, Maynor and Ellch were able to discover many examples of wireless device driver flaws, including one that allowed them to take over a laptop by exploiting a bug in an 802.11 wireless driver. They also examined other networking technologies including Bluetooth, Ev-Do (EVolution-Data Only), and HSDPA (High Speed Downlink Packet Access).

The two researchers declined to disclose the specific details of their attack before the August 2 presentation, but they described it in dramatic terms.

"This would be the digital equivalent of a drive-by shooting," said Maynor. An attacker could exploit this flaw by simply sitting in a public space and waiting for the right type of machine to come into range.

The victim would not even need to connect to a network for the attack to work.

"You don't have to necessarily be connected for these device driver flaws to come into play," Ellch said. "Just because your wireless card is on and looking for a network could be enough."

More than half of the flaws that the two researchers found could be exploited even before the wireless device connected to a network.

Wireless devices are often configured to be constantly sniffing for new networks, and that can lead to security problems, especially if their driver software is badly written. Researchers in Italy recently created a hacking lab on wheels, called project BlueBag, to underscore this point by showing just how many vulnerable Bluetooth wireless devices they could connect with by wandering around public spaces like airports and shopping malls. After spending about 23 hours wandering about Milan, they had found more than 1,400 devices that were open to connection.

"Wireless device drivers are like the Wild, Wild West right now," Maynor said. "Lorcon has really brought mass Wi-Fi packet injection to script kiddies. Now it's pretty much to the point where anyone can do it."

Part of the problem is that the engineers who write device drivers often do not have security in mind, he said.

A second problem is that vendors also make devices that go beyond the requirements of a particular wireless standard. That piling on of features can open security holes as well, he said.