A group of seven computer scientists have discovered WindTalker, a vulnerability in Wi-Fi networks that lets hackers potentially read keystrokes based on the finger position of a cellphone or tablet user.

The vulnerability was found by five researchers based at Shanghai Jiao Tong University in Shanghai, China, while the other two are affiliated with the University of Massachusetts at Boston and University of South Florida in Tampa, Fla.

Xiaohui Liang, the researcher based at UMass Boston, says by exploiting this vulnerability hackers can know when the user inputs PIN numbers. The researchers recently presented their findings in a paper to the ACM SIGSAC Conference on Computer and Communications Security in Vienna, Austria.

Paul Ducklin, a senior technologist at Sophos who wrote a blog about WindTalker, says the research is important in that it points at a previously undiscovered vulnerability.

“This research just underscores that security is a journey,” Ducklin says. “While this couldn’t have been possible five years ago, with the processing power now available, it is today. And while manufacturers don’t have to run out quickly to correct WindTalker, it does put them on notice that it could be a problem in the years to come.”

In his blog, Ducklin explains that the researchers used specially modified firmware downloaded into a single Wi-Fi network card to create an access point that could keep track of minute variations in the underlying communication signal, and correlate those changes with the cell phone user’s typing.

Ducklin says once the researchers detected the Wi-Fi flaw, they also realized that hackers can set up rogue networks in situations where users sign on automatically. This can be on a public Wi-Fi network at a coffee shop or airport, or even a home network where users generally sign on without looking at the network’s name.

“The criminals can clone the network’s name and the user would have no idea if it was the legitimate network,” Ducklin says.

Ducklin praised the researchers for discovering this new flaw, saying that users may now realize that they have to take added precautions. He recommends that users consider installing a VPN client on their devices, as well as using two-factor authentication.

“The two-factor authentication can’t prevent a hack, but it can mitigate the damage,” he explains. “While a hacker may get through once, with two-factor authentication, the password that the criminals used today won’t be any good tomorrow.”

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