(Bloomberg) -- Fiat Chrysler Automobiles NV is recalling about 1.4 million cars and trucks equipped with radios that are vulnerable to hacking.

The company said in a statement it has blocked unauthorized remote access to certain vehicles systems with a network-level improvement on Thursday.

Fiat Chrysler was already distributing software to insulate connected vehicles from illegal remote manipulation after Wired magazine published a story about software programmers who were able to take over a Jeep Cherokee being driven on a Missouri highway. Fiat Chrysler reiterated that it’s not aware of any real-world unauthorized remote hack into any of its vehicles.

It stressed that no defect was found and that it’s conducting the campaign out of "an abundance of caution."

The recall covers almost a million more models than those initially identified as needing a software patch. The action includes 2015 versions of Ram pickups, Jeep Cherokee and Grand Cherokee SUVs, Dodge Challenger sports coupes and Viper supercars.

Affected customers will receive a USB device to upgrade their vehicle’s software with additional safety features, beyond the network-level measure.

Shares of Fiat Chrysler fell 1.4 percent to $15.32 at 11:07 a.m. New York time. The stock had gained 34 percent this year through Thursday.

Special Reports /

Fiat Chrysler recalls 1.4 million autos for hacking defense

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