"In past research, Guri and his team at the Ben-Gurion university's Cyber-Security Research Center have shown that attackers could steal data from secure systems using a plethora of techniques such as:
LED-it-Go - exfiltrate data from air-gapped systems via an
HDD's activity LED
USBee - force a USB connector's data bus give out electromagnetic emissions that can be used to exfiltrate data
AirHopper - use the local GPU card to emit electromagnetic signals to a nearby mobile phone, also used to steal data
Fansmitter - steal data from air-gapped PCs using sounds emanated by a computer's GPU fan
DiskFiltration - use controlled read/write HDD operations to steal data via sound waves
BitWhisper - exfiltrate data from non-networked computers using heat emanations
Unnamed attack - uses flatbed scanners to relay commands to malware infested PCs or to exfiltrate data from compromised systems
xLED - use router or switch LEDs to exfiltrate data
aIR-Jumper - use a security camera's infrared capabilities to steal data from air-gapped networks
HVACKer - use HVAC systems to control malware on air-gapped systems
MAGNETO & ODINI - steal data from Faraday cage-protected systems
MOSQUITO - steal data from PCs using attached speakers and headphones
PowerHammer - steal data from air-gapped systems using power lines
CTRL-ALT-LED - steal data from air-gapped systems using keyboard LEDs
BRIGHTNESS - steal data from air-gapped systems using screen brightness variations