Tracking Android phones is easy, says researcher

Assisted-GPS a boon for surveillance

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To save time, battery life and processor cycles, smartphones don’t rely on “pure” GPS to fix their locations – they get help from location data in the mobile network. Research presented at Black Hat in Las Vegas last week cautions users that this represents a serious security vulnerability.

Under A-GPS (Assisted-GPS) schemes, the network can send current satellite location and time to the receiver, letting it acquire the signals more quickly; or the device can provide its GPS signal data to a server in the network for faster processing. Either way, the technology depends on the handset asking the network for help - and when that happens, location data is exchanged over the network.

The problems, according to University of Luxemboug researcher Ralf-Philipp Weinmann, are that requests for help are sent in the clear and are apparently easy to hijack.

For example, if an attacker had access to a WiFi network the phone connected to, its assistance request could be captured, and redirected to the attacker’s server. The attacker would now know where the phone is, and worse, that redirection would stay in place wherever the phone went in the future.

According to Technology Review, Weinmann described the attack as “rather nasty” since “if you turn it on just once and connect to that one network, you can be tracked any time you try to do a GPS lock”.

Because the processing is often handed off to the device’s main processor, Weinmann says, it could also act as a gateway for other attacks, from crashing the target device to planting malware. ®

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