Skeptics Guide to the Universe #607 – Science or Fiction. Steve used the word only to describe capturing data from the LED on the computer. Using malware in addition to the LED is not only using the LED. If you add the variable of freighted malware to the possibilities, there are many ways that information from your computer could be gathered, even if it was never connected to a network.
The only way to be certain that your code is clean is to write every bit of the code yourself on an isolated machine, and even then malware can be encoded onto the ROM chips built into the board.
Basically, if you want certainty that your systems are secure, you are screwed. But malware in addition to the LED is still not only using the LED.
(letter to Dr. Steven Novella, host of the SGU)