There is a question which in an HVAC system is more important: data exfiltration or availability.

Usually what’s conspicuous is data relating to security. However, the answer is “availability” even though maybe it only accounts for 51% of the answer. That’s because “availability” is the main function of an HVAC system and also one of the three vertices of the security triangle CIA.

The HVAC system is really only in one large physical data center. Here we illustrate its “mini version” which is the cooling system of a computer

It is a liquid-based cooler. The display that indicates the cooling temperature (or CPU temperature or temperature elsewhere) is not just decorative, it “talks”, making it highly effective in monitoring system availability.

If the temperature is abnormally high, it is likely that there is a resource consuming process or malicious network traffic.

Almost every motherboard has a temperature entry point for a two-pin jack. You can purchase a temperature sensor for $1 to plug it in

In the picture above, the white two-pin jack is being connected to the mainboard. You can place the sensor head anywhere you want to get the temperature you need.