(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.

[Related: Fiat Chrysler offers software patch after hackers control Jeep]

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.

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