"That's no different from pouring sugar into a vehicle's gas tank. All you need is physical access. Valasec and Miller are good about getting headlines," Allen said. "They did have physical access to the vehicle before they hacked it."
Miller said the Chrysler Jeep Cherokee belonged to him, but prior access to the vehicle was not needed for the zero day-style attack to take place.
"We could have easily done the same thing on one of the hundreds of thousands of vulnerable vehicles on the road," Miller said. "We gained access by exploiting a vulnerability that was present on the head unit (i.e. the radio/navigation thingie) that was accessible over the Internet. It did not require any physical access or changes to the vehicle."
The attack, will work on any Chrysler vehicle with the Uconnect telematics system from late 2013, all of 2014, and early 2015 -- that includes Dodge, Ram and Jeep model vehicles.
The physical equipment needed to perform the vehicle hack was relatively simple: Miller and Valasek used a Kyocera Android smartphone as a W-iFi hotspot connected to a MacBook laptop. The head unit on the Chrysler was linked to the Internet by Sprint's cellular network.
Vehicle manufacturers routinely collect information on vehicles through cellular networks in order to alert drivers that maintenance or repairs may be required. Today, more vehicle manufacturers are also embedding Wi-Fi routers to enable mobile Internet connectivity.
Miller said his Jeep Cherokee has a Wi-Fi option, but that it's the cellular function that allows access from anywhere.
Through the cellular connection, Miller and Valasek are able to gain a vehicle's GPS coordinates, vehicle identification number, and, more importantly, its IP address.
Miller said the vulnerability that allowed the attack is exclusive to Chrysler's UConnect head unit, but there are likely similar types of security holes on other vehicles' telematics systems.
Miller and Valasek have been communicating their research with Chrysler for the past nine months or so, which allowed the company to release a software patch to help prevent future attacks.
Ron Montoya, consumer advice editor with Edmunds.com, said he was surprised physical access was not required for the vehicle hack, but he also doesn't think hacking a vehicle is as easy as it may seem.
"This is a group of researchers that have been dedicating their lives the past couple of years to doing this, and they have very high skill levels. They're security engineers," Montoya said. "I don't think this is something to freak out over. It does [give] awareness to automakers that they need to take a hard look at security on their vehicles."
To create more secure vehicles, Montoya believes manufacturers must ultimately find a way to isolate driving functions from infotainment systems.
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