Silence on the Wire

Food for Thought

Other than network device LEDs, plenty of other, equally interesting light emissions leak scenarios can be found, although the amount of information disclosed can be significantly lower. For example, consider disk activity LEDs. Of course, disk communication is not using serial signaling; instead, portions of data, ranging from bytes to 32-bit words, are sent simultaneously using a set of signal lines. And, although the LED is usually attached to indicate only a state of a specific control line, it is still possible to deduce many aspects of system activity by measuring seek times or the amount of data stored and read. (Depending on what the LED is actually attached to, it may be possible to measure either or both.) Although it’s ...