Laser listening devices (laser microphones) are a well understood technology. They have historically been used in the surreptitious surveillance of protected spaces. Using such a device, an attacker bounces an infrared laser off of a reflective surface, and receives the ricocheted beam with a photoreceptor. If the beam is reflected from a surface that is vibrating due to sound (voice is a typical background target), that sound is subsequently modulated into the beam and can be demodulated at the receptor. This is a known attack method and will be briefly discussed. However, does this principle also hold for non-amplified or naturally concentrated light sources? Can one retrieve modulated audio from reflected sunlight? The idea of modulating voice with sunlight was pioneered by Alexander Graham Bell in 1880 with an invention called the Photophone. A Photophone uses the audio modulation concept now used in laser microphones, but relied on a concentrated beam of sunlight rather than a laser to communicate at distance. Considering that Bell proved that intentionally concentrated sunlight can be used to modulate voice, we will explore under what natural conditions modulated audio can be found in reflected ambient light. Using off the shelf solar-cells and handmade amplifiers, Erik will demonstrate the use of the receiver side of a historic Photophone to identify instances of modulated audio in reflected light under common conditions.

Erik Kamerling is a Senior Director at The Center for Internet Security, in the Multi State Information Sharing and Analysis Center (MSISAC). He has nineteen years of experience in the fields of advisory and consulting, network security assessment, penetration testing, vulnerability research, monitoring/incident response, and fundamental security research. He?s made the rounds over the years, having worked for RSA, Mandiant, Neohapsis, and Symantec (Bugtraq/Security Focus). His work has taken him around the globe conducting assessments, consulting, and research for government and private industry alike. He enjoys writing and research on cyber intelligence topics and has driven the development of keynote speeches, research presentations, course-ware, advisories, papers, and hacking and penetration testing classes taught in a variety of venues. He spends his spare time researching and working on new techniques in information hiding, detection evasion, communications subterfuge, parasitic computing, and vulnerability identification.

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