Just days before a tens of thousands of computers in homes, business and government were infiltrated by malicious software, scientists warned Wi-Fi routers, the kind found in most Australian homes, present a major security risk.

Scientists for the first time produced a hologram using a wi-fi transmitter – instead of using a laser – furthering the growing research into wi-fi being used to spy  through walls.

Holograms, of the sort made famous by Princess Leia in Star Wars are usually made by lasers, which produce what’s known as ‘coherent light’ in the form of beams.

German physicists from the Technische Universität München recognised that systems such as Wi-Fi or Bluetooth emit coherent light in the form of radio waves or electromagnetic radiation.

People could be able to peer into your home using wi-fi technology.

Which means that the radio waves coming out of every commercial Wi-Fi router – sitting on a kitchen bench or loungeroom cabinet – are constantly making a hologram of all the objects in the room the router occupies.

Dr Friedemann Reinhardat, an expert in quantum sensors, and Philipp M. Holl, an undergraduate student, proved the theory by recording the shape of a metre-wide aluminium cross by using two receivers that scanned for the radio waves.

The process involved using a version of synthetic aperture radar – the same technique used to make 3D images of mountain ranges on earth from spacecraft.

By running the recorded radiation backwards in time, in a computer, a 3D reconstruction of the cross came into being on the computer screen.

Wi-fi breakthrough

Science magazine, which reported the breakthrough early last week, noted that, “in principle, the technique could enable outsiders to ‘see’ the inside of a room using only the Wi-Fi signals leaking out of it, although some researchers say such spying may be easier said than done”.

However, in August, The Atlantic published a summary of US, Chinese, British and Australian research projects that all enjoyed breakthroughs in spying on people using Wi-Fi radiation.

Four years ago, Fadel Adib and Dina Katabi, researchers from MIT’s Computer Science and Artificial Intelligence Lab (CSAIL), used radio waves from a router to detect the number of humans in a room and identify basic hand gestures, through a wall and a solid wooden door.

They gleefully published their experiments in a paper titled See Through Walls With Wi-Fi!.

In 2015, Adib and Katabi, having refined their sensors, developed technology that can distinguish between different people standing behind walls, and remotely monitor breathing and heart rates with 99 percent accuracy.

They packaged the technique into a device called Emerald for aged care facilities, to detect movement and falls by elderly residents. The device has had some success in predicting falls before they happen by developing a profile of a resident’s movement patterns.

The researchers gave a demo of Emerald to then-President Barack Obama. They were hailed for doing good.

Not so benign is emerging technology where Wi-Fi radio waves allow lip-reading, from behind a wall, with almost perfect accuracy.

Moving lips, like moving limbs, alter the shape of the Wi-Fi radio waves with which they’re unwittingly interacting.

As scientists refine their measurements, the more detail your life and doings can eventually be captured by people parked in the street outside your house.