Hackers can influence real-time traffic-flow-analysis systems to make people drive into traffic jams or to keep roads clear in areas where a lot of people use Google or Waze navigation systems, a German researcher demonstrated at BlackHat Europe.

Google and Waze both offer turn-by-turn navigation in smartphone apps and use information derived from those phones for real-time traffic analysis. However, because of the tradeoff between user privacy and data gathering, hackers can anonymously influence navigation software to trick the real-time traffic system into registering something that isn't there, said Tobias Jeske, a doctoral student at the Institute for Security in Distributed Applications of the Hamburg University of Technology, during the security conference in Amsterdam.

"You don't need special equipment for this and you can manipulate traffic data worldwide," Jeske said.

Both Google and Waze use GPS as well as Wi-Fi in phones to track locations. If Wi-Fi alone is enabled, only information about wireless access points and radio cells in the surrounding area will be transferred, which lets the navigation systems approximate the location of the user, Jeske said.

Google navigation uses real-time traffic information in Google Maps for mobile. The protocol used to send location information is protected by a TLS (Transport Layer Security) tunnel that ensures the data integrity so that it is impossible for an attacker to monitor a foreign phone or modify information without being detected by Google, said Jeske. However, TLS is useless if the attacker controls the beginning of the TLS tunnel, he added.

To be able to control the beginning of the tunnel, Jeske performed a man-in-the-middle attack on an Android 4.0.4 phone to insert himself into the communication between the smartphone and Google. When the attacker controls the beginning of the tunnel, false information can be sent without being detected and in this way attackers are able to influence the traffic-flow analysis, according to Jeske.

If, for example, an attacker drives a route and collects the data packets sent to Google, the hacker can replay them later with a modified cookie, platform key and time stamps, Jeske explained in his research paper. The attack can be intensified by sending several delayed transmissions with different cookies and platform keys, simulating multiple cars, Jeske added.

An attacker does not have to drive a route to manipulate data, because Google also accepts data from phones without information from surrounding access points, thus enabling an attacker to influence traffic data worldwide, he added.

A similar attack scenario can be applied to Waze, but it is more difficult to affect the navigation of other drivers, Jeske said. Waze associates position data with user accounts, so an attacker who wants to simulate more vehicles needs different accounts with different email addresses, he added.

Jeske also found a way to transfer position data to Waze without user authentication, rendering the attacker anonymous, he said, without elaborating on that method.

For an attacker to actual influence traffic, a substantial number of Waze or Google navigation users have to be in the same area. When it comes to Waze, that is probably not going to happen, for instance, around Hamburg, he said. Waze, however, had 20 million users worldwide in July last year, so there should be areas where it is possible, he said.

Although Jeske hasn't tested the vulnerability of other services offering real-time traffic data, they work more or less the same way as Google and Waze, so he expects that similar attacks on those systems are possible, he said.

Companies that offer navigation apps can avoid this sort of attack by linking location information to one-time authentication that is time stamped and limited to a fixed amount of time, Jeske said. That would restrict the maximum number of valid data packets per time and device, helping to secure the system, he added.

Loek is Amsterdam Correspondent and covers online privacy, intellectual property, open-source and online payment issues for the IDG News Service. Follow him on Twitter at @loekessers or email tips and comments to loek_essers@idg.com