Shh.... Hear that? It's the sound of silence.

And that's why you won't know if a hacker is controlling your phone via Siri or Google Now through radio waves.

Wired reports that a group of researchers at France's government information security group found a way to silently send commands to nearby iOS and Android smartphones. I wouldn't panic just yet because the tools they needed are a full laptop and antenna but the team says their kit could fit into a backpack and you'd never know.

The attacking method uses connected headphones in an iPhone or Android handset to act as a receiving antenna; similar to how FM radio chips do so inside mobile devices.

With the open source GNU Radio software on a laptop, electromagnetic signals can be sent to those devices. Depending on the sent command, Siri or Google Now can told to open up a website, send a text, place a call or do any other number of things.

Granted, most handset owners don't have wired headphones plugged into them when not in use. And if someone was remotely sending silent "voice" commands to your phone, you'd likely see what's going on; the hack doesn't disable the handset's display.

Even so, it's a concerning proof of concept that both Google and Apple should consider researching and finding a way to close the door on any potential unwanted access. The researchers say they have shared their information with both companies.

In a demonstration of the remote control, the researchers were about six feet from a phone. They say that with more battery power and a stronger antenna, the exploit could occur in up to a 16 foot range. The equipment to do so wouldn't be as portable, however.