Computer Components: Follow the Data Through the Machine

Before you can secure a computer, you need a mental model of what the major components do.

For this course, start with five parts:

• input
• memory
• CPU
• output
• motherboard and connected storage/devices

The model is simplified, but it gives you enough structure to explain where data moves and where failures can happen.

Input

Input devices provide data or commands to the system.

Examples:

• keyboard
• mouse or touchpad
• microphone
• camera
• network interface
• sensors

From a security perspective, ask:

• Can the input be trusted?
• Is the device authorized?
• Can software receive more input than it should?

Memory

RAM holds active program state and data while the computer is running.

It is fast and temporary compared with long-term storage.

If a system runs many applications at once, RAM helps hold their active state.

Security questions include:

• Which process should be able to access which data?
• What happens if sensitive information remains in memory longer than expected?
• What happens when memory is exhausted?

CPU

The CPU executes instructions.

It does not "know" whether an instruction is helpful or malicious. It executes according to the software and privilege context the system provides.

That is why software integrity, permissions, and privilege boundaries matter.

Storage

Storage preserves data after power is removed.

Examples include solid-state drives and other persistent media.

Security questions include:

• Is sensitive data encrypted?
• Who can read or modify the files?
• Are backups available?
• What happens if storage fails?

Output

Output devices present results:

• display
• speakers
• printer
• network transmission
• actuator or connected device

Output can also leak information. A screen, printer queue, or network message can expose data to the wrong audience.

Motherboard and buses

The motherboard connects major components and provides communication pathways.

For this introductory model, think of it as the physical platform that lets CPU, RAM, storage, and connected devices exchange data.

Trace one action

Scenario:

A student opens a saved image and displays it on screen.

Build a trace:

1. operating system receives the open request
2. data is read from storage
3. active data is placed in memory
4. CPU executes instructions from the image-viewing software
5. graphics/output system produces the visible result

Your trace does not need to model every electrical detail. It should show the relationship among the major components.

What can go wrong?

For each component, identify one availability, integrity, or confidentiality failure.

Add CPU, output, motherboard/network interface, and one other component.

Evidence for Lesson 1

Submit:

• labeled computer-component diagram
• one complete data-flow trace
• component/failure/CIA table
• one paragraph explaining why the CPU executing an instruction does not prove the instruction is trustworthy

Finish with:

The component I used to think of as "just hardware" but now see as a security boundary is ________.