Apple's personal assistant Siri can be controlled by hackers through voice instructions given to her remotely, French researchers recently discovered.

Wired noted French agency ANSSI researchers found out that "they can use radio waves to silently trigger voice commands on any Android phone or iPhone that has Google Now or Siri enabled."

The exclusive report added that this could be made easier if a headphone or a microphone is attached to the phone.

In explaining the possibility, the researchers mentioned that the headphones can be used to convert the electromagnetic waves of the antenna into signals "that appear to the phone's operating system to be audio coming from the user's microphone."

From afar, hackers now has the ability to instruct the personal assistant system to call, send a text and even monitor e-mails and other important correspondence.

"The possibility of inducing parasitic signals on the audio front-end of voice-command-capable devices could raise critical security impacts," said French researchers José Lopes Esteves and Chaouki Kasmi in the Wired report.

On the other hand, research group director Vincent Strubel explained that anything can be done using this possible hack.

"The sky is the limit here. Everything you can do through the voice interface you can do remotely and discreetly through electromagnetic waves," he added.

The Verge, however noted that there can be limitations to this possibility since it requires a microphone and earphones.

"There's also a problem of range. Using equipment small enough to fit into a backpack, the researchers were able to make the hack work over a distance of just 6.5 feet," it added.

If the equipment would have been bigger to fill a car, The Verge said the estimated distance for it to work would be about 16 feet only.

Since the possibility of this personal assistant hack has been exposed, iMore said users can set "custom trigger words" to avoid this from happening though it said that this is only possible with Android devices for now.

Another prevention measure is to enhance shielding on your headphone cords.

"Though no doubt an expense, even if only the most popular brands implemented that, it would reduce the surface potential of the 'hack,'" iMore added.

Also, PC Mag said that users should be conscious with what is happening with their phones and check if there browsers are mysteriously opened or there are messages sent that you do not know of.

There is still no official world from Apple and Google on the recent issue but iMore said that users need to be informed of such risks but these should also not be sensationalized.

"Security and convenience are almost always at odds. Siri, Google Now, "Hey Siri", and "Okay Google Now" provide for increased convenience at the expense of some security. If you don't use or need voice activation or Lock screen access, by all means turn them off," iMore suggested to users.