Solve : Embedded Microcontroller devices inside the PC.?

This post is a very brad consideration of Embedded Systems/8051 Micro controller and similar devices.
Please bear with me.
Introduction:
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The Intel 8051 micro controller is one of the most popular general purpose micro controllers in use today. The success of the Intel 8051 spawned a number of CLONES which are collectively referred to as the MCS-51 family of microcontrollers, which includes chips from vendors such as Atmel, Philips, Infineon, and Texas Instruments.

http://en.wikibooks.org/wiki/Embedded_Systems/8051_Microcontroller
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Typical applications
8051 chips are used in a wide variety of control systems, telecom applications, robotics as well as in the automotive industry. By some estimations, 8051 family chips make up over 50% of the embedded chip market.

Relevance to PC USERS:
So what relevance does this have on our present day personal computer experience? More that one might guess. For one, such devices are used to mass-produce modern computer COMPONENTS. Furthermore, some parts of a modern desktop, laptop or table will contain a micro controller in addition to the main CPU of the device.
Such is needed to manage memory, refresh the display or connect to Wi-Fi. The keyboard has a micro controller. So does your mouse.

Recently attention was drawn to the USB controllers used in one particular brand of USB thumb drive. It was hard to understand that a simple device could hide a virus in such a way the most AV programs could not find it. One reason is that the details of the micro-controller used are not published. Therefore an AV program does not know how to read the hidden information.

But the PROBLEM, if it is real, would not be limited to just USB devices. MCUsa are in printers, modems, routers and microwave overs.

Each manufacturer of a micro controller can have there own set of codes use to hide accede to the programmable memory area. The are dozens of different manufacturers and each can have several variations on designs.

A few companies are:
(Major semiconductor firms Sales rank 2011 )
Intel Corporation
Samsung Electronics
Texas Instruments
Toshiba Semiconductor
Renesas Electronics
Qualcomm
STMicroelectronics
Hynix
Micron Technology
Broadcom
AMD
Infineon Technologies

Of course the list goes on and on. The above is just the big ones. Theyall have some kind of controllers in the product line.

For example, AMD makes a micro controller the uses the same code as the x86 family of CPUs.
Gizmo board tiny AMD powered x86 MCU. Video
Yes, the AMD board is a real overkill for most applications. Where low-power and low speed are needed a micro controller can be the size of a girl's fingernail.

So what is the point of this? There was a general concept that all electronics devices other that TM and the CPU were permanent t non-programmable circuits. It was thought by many that software could only change RAM and and hard drive data. Not true. Most of the micro controllers in use today can be re programed by software alone. If it has have the codes.
It has been suggested that manufacturers should use heavy encryption to make it very hard for even professional hackers to get into the controllers without prior knowledge of the codes.

However, many believe this is a false alarm. Many are confident that the present AV programs are good enough and it is not likely any group of hackers will make a huge effort to learn how to program controllers to support malware.
Do you have any knowledge of how to program micro controllers?
If so, what is possible? What is likely?