Modified E-ZPass Detects Reads Far From Toll Booths

Def Con speaker [pukingmonkey] has spent considerable time studying the methods used by government and law enforcement agencies to track private citizens’ vehicles on the road. One of the primary tracking methods is E-ZPass, an electronic toll collection system used in several states across the country. [pukingmonkey] opened his E-ZPass tag to find a relatively simple circuit. in his DEF CON presentation (PDF), it notes that you shouldn’t do this with your own tag, since tags aren’t legally owned by the user.

The tag uses a long life 3.6 volt battery to operate. When inactive, the tag draws only 8 microamps. During reading, the current consumption jumps to 0.3 mA. Armed with this information, it was relatively easy to add a current sense circuit that outputs a pulse when a tag is read. The pulses are then fed into a toy cow that lights up and “Moo” with each reading.

After completing the tour, it was time for a little drive around New York. in [pukingmonkey’s] quite a harrowing drive between times square and madison square garden (non-taxi route) the cow was milked 6 separate times. The New York City Department of Transportation has long said these readings are only used to track congestion. However, we would recommend placing your tag in an anti-static bag (Faraday cage) when not approaching a charge.

[via Boing Boing]

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