Scientists have for the first time demonstrated that it is possible to covertly siphon sensitive files, passwords or other critical data from any common router.
Researchers at the Ben-Gurion University of the Negev (BGU) in Israel demonstrated how functionality light-emitting diodes (LEDs) can be silently overridden by malware they developed (code named "xLED"), which infects firmware in the device.
Once the xLED malware infects the network device, it gains full control of the LEDs that flash to indicate status.
Network devices such as routers and local area network switches typically include activity and status LEDs used to monitor traffic activity, alerts and provide status.
"Sensitive data can be encoded and sent via the LED light pulses in various ways," said Mordechai Guri, head of research and development at the BGU Cyber Security Research Center (CSRC).
"An attacker with access to a remote or local camera, or with a light sensor hidden in the room, can record the LED's activity and decode the signals," said Guri.
"Unlike network traffic that is heavily monitored and controlled by firewalls, this covert channel is currently not monitored," said Guri.
"As a result, it enables attackers to leak data while evading firewalls, air-gaps (computers not hooked up to the internet) and other data-leakage prevention methods," he said.
The xLED malware can programme the LEDs to flash at very fast speeds – more than 1,000 flickers per second for each LED.
Since a typical router or network switch includes six or more status LEDs, the transmission rate can be multiplied significantly to as much as thousands of bits per second.
As a result, a significant amount of highly sensitive information can be encoded and leaked over the fast LED signals, which can be received and recorded by a remote camera or light sensor.