What design flaw would allow a computer virus to significantly damage or destroy computers on a hardware level?
Normally computer viruses are designed to steal information and affect things largely on the software level. Rarely do we see actors trying to outright destroy computers using a virus. However, that is exactly what I am going for. In this situation, such a virus is being released as part of warfare operations against enemy computer systems.
Some hardware-based viruses work on manipulating a programmable logic controller. Essentially the sections that handle instructions for smaller subsystems on a motherboard or system can cause issues by exploiting vulnerabilities in an operating system. These attacks are designed to create a physical action that adversely affects a computer. For example, reducing fan speeds to cause thermal runaway, cause a hard drive's mechanical arm to switch back and forth constantly, excessive reads and writes to an SSD and more will destroy parts of a computer.
Hardware Trojans exist on a circuity/integrated circuity level. Essentially a piece of grafting or extra hardware placed onto a board to allow the running of malicious remote software or pre-loaded instructions.
Similarly, a firmware-based virus can render entire memory banks infected in ways that can't be solved easily short of a firmware or hardware update completely.
While devastating, hardware-based viruses are incredibly expensive to make. 81
They are also generally targeted against very specific systems (see Stuxnet). There are also numerous motherboard fail safes that have been built in to stop things such as power surges or thermal throttling. Even microcontrollers these days have ways of checking to see if something running is about to brick a system.
For the purposes of this question one can assume most motherboards are built in a very similar manner with an overall shared design layout. While sizing and certain portions may be different between boards, it's safe to assume that the PCB's share a lot of common features. One can also assume that no computer is air gapped for the purposes of this question.
What design flaw would allow a computer virus to consistently destroy computers at a hardware level such that entire computers need to be thrown away and redesigned from the ground up?
The computer virus in question can be deployed in multiple ways and can be constantly updated. They can utilize things like AI and can tell if they are being executed in a virtual machine or not. Among other things. The virus in question is exploiting the design flaw in such a computer system, systems that don't share the same issue (like say a calculator or LED light) are not within the scope of the question. 81