For some reason I just noticed this posting.
   One partial solution to exfiltrating information by LEDs would be to
   design the LEDs with capacitors across them, greatly reducing the rate
   of change of intensity.   This could also be retrofitted after
   assembly.
   In 1977, after building a "Dyna-Micro" Single-board computer
   (highlighted in Radio-Electronics magazine) I noticed that a nearby  AM
   radio could easily pick up RF from it.  If anything, this is
   potentially an even more useable kind of surveillance, because it
   doesn't necessarily require intrusion into a computer room or building.
                       Jim Bell

   On Tuesday, May 5, 2020, 06:04:29 AM PDT, grarpamp <grarpamp@gmail.com>
   wrote:
   [trim]
   LED-it-Go - exfiltrate data from air-gapped systems via an HDD's
   activity LED
   [trim]
   xLED - use router or switch LEDs to exfiltrate data
   [trim]
   CTRL-ALT-LED - steal data from air-gapped systems using keyboard LEDs