Computer Systems

Computer Systems

1. Hardware

   • Vital
     • CPU
       • Von Nuemann
       • Harvard
       • Cache
       • Quality
         • Clock Speed
           • MHz: 1,000,000 instructions processed per second
           • GHz: 1,000,000,000 instructions processed per second
         • Cores
         • Threads
           • Multi threading
             • Software: Hyper-threading
               • Advantages: Balanced performance in both multi and single threaded programs.
               • Disadvantages: Simulated multithreading can't reach hardwired multithreading CPUs potential due to software limitations.
             • Hardware: More than one logical core for each physical core
               • Advantages: Excels in multithreaded programs and actions compared to software based multithreading.
               • Disadvantages: Processes single threaded applications and programs slower than other CPUs.
                 • Analogy
                   • Imagine giving two students a maths question, but they only have one pen.
       • Contents
         • Algorithmic Logic Unit
         • Control Unit
           • Works with the ALU to control the flow of data within the system and to decode instructions
     • Graphics Card
     • Motherboard
       • System Speaker
         • Purpose: Gives user BIOS beep codes, to show whether the system passes the POST, or encounters errors. This is used incase the monitor cannot display the error, and so the computer manually makes sounds with a buzzer to send a message.
     • Network Interface Card
     • PSU
     • RAM
     • Storage
     • Cooling System
       • Air
         • Stock
         • Separate
       • Liquid
         • Water pump
         • Cryogenic fluid
           • Liquid nitrogen
     • CMOS Battery
       • This is the battery in charge of keeping the registers and chips with extra BIOS information, removing this battery presents a security issue.
   • Peripherals
     • Input
       • Mouse/Keyboard
       • Trackpad
       • OCR
     • Output
       • Touchscreen
       • Speaker
         • COMMON MISCONCEPTION: THIS IS NOT THE SYSTEM SPEAKER
       • Monitor
         • DISPLAY
           • Resolution
             • Refresh rate
               • Hz
           • LCD/LED
             • Liquid Crystal Display
             • Light Emitting Diode (Display)
               • OLED
                 • Organic LED (Display)
               • AMOLED
                 • Active Matrix Organic LED (Display)
       • Printer
   • Basics

2. Software

   • Drivers
   • OS
     • Linux
     • Windows
       • S
       • Core
     • OSX
     • ChromeOS
     • PC/Tablet
     • Mobile
       • iOS
       • Android
       • Windows 10 Mobile
   • Programs
     • Architecture
       • x32
       • x64
       • x86
   • Utilities

3. Systems

   • Control Systems
   • Dedicated
   • Control
   • Embedded

4. Memory and Storage

   • Primary
     • RAM
       • VOLATILE: Needs power to maintain data.
       • RAM is slower than cache, But a LOT faster than secondary storage.
     • ROM
       • Holds the boot sequence
         • Stores the BIOS
           • Test the memory
           • See what hardware is present
           • Copy the OS over to the RAM
       • NON-VOLATILE: Does not need power to maintain data.
       • It usually comes on a small, factory made chip, built into the motherboard.
       • You can flash the ROM
   • Secondary
     • Long term storage
     • Holds the programs
     • Virtual Memory
       • This tricks the computer into thinking there is more RAM, to the compromise of losing secondary storage space
   • Storage devices
     • Capacity
     • Speed
     • Durability
     • Portability
     • Reliability
     • Magnetic Hard Drives
       • 5400 - 15000
     • Solid State Drives
       • No moving parts
       • Faster R/W speeds than HDDs
       • Silent
     • Hybrid
     • Optical disc
       • Compact discs
         • 700MB
         • DVD
           • 4.7GB
         • Blu-ray
           • 25GB
   • Tertiary
     • Magnetic tape

5. Malicious Threats and Resolutions

   • Virus
     • BIOS
       • Bricked Motherboard
   • Browser Hijackers
     • Usually harmless, these programs burrow deep into the computer and trigger adware pages to come up at certain times.
     • Fixes
       • Manual
         • Manually removing these programs is not recommended, since they are buried into the OS code. To manually remove a program, the user must start up the PC in safe mode with basic drivers, try to locate a suspicious program with an advanced forensics program such as Volatility, find the PID and remove the program. However, if the wrong program is deleted, a clean install is necessary or, worst case scenario, a piece of hardware malfuntions due to, say, the fan regulation program is down.
       • Automatic
         • Using a specialised utility to carefully remove the rogue program is recommended, since the program recognises what is an innocent, default program and what is suspicious. It will also log the programs previous activity and check if it matches the intervals of the webpages. Then, with the precision of a scalpel, it cautiously removes the program step by step, just in case the hijacker was designed to resist removal.
   • Trojans
     • This malware often masks its existence as the existence of other software, making it hard to locate. It is simply a masked virus.
     • Fixes
       • Recognize the Trojan: After recognizing a file infected with Trojan horse, it becomes easy to remove it. Usually, your system will give you DLL error, which is associated with Trojan attack. You can copy the error and find out about the affected executable file online. Stop the function of system restore: If you forget this step, then it will restore the files you will delete. Restart you computer: when you restart, press F8 and then select safe mode. Go to Add or Remove Programs in the control panel, and then remove the programs affected with Trojan horse. Remove extensions: To delete all files of a program, you should remove them from Windows System folder.
   • Rootkits
     • This program is a collection of computer software, typically malicious, designed to enable access to a computer or areas of its software that would not otherwise be allowed.
   • Ransomware
     • One of the most devastating types of malware to enterprises and small businesses alike. This is practically a way for someone to cruelly test whether a company backs up its data or not. If the answer is the latter, the user faces two options:
       • Send a sum of cryptocurrency to the hacker's wallet
         • Many officials and professional malware removal personell advise not to give in to the tempting "fine" of the hacker. This is because they will usually leave the drive encrypted and ask for a larger sum, or leave a subtle script on the drive to run x days after "decryption". The user faces the same problem, even if the company backs up, because the backups are also infected.
       • The drive(s) will stay encrypted and all data is practically useless.
         • All those priceless spreadsheets and important files are gone. The company is ruined or has a major setback.
     • Fixes
       • Not exactly a fix, but the reason ransomwares usually target businesses and workstations is because the files are of value to the user(s). If the user is a casual laptop user ,who browses the web, or is a gamer, the files are not so valuable. Most game progress is saved on servers these days and so, even though a clean install and drive wipe is a chore, after a couple of hours, the exact same machine will be up and running again. Other than that, these programs encrypt so strictly, and follow a hardwired protocol so they can't be brute forced to decrypt, there is no hope at most times.

Images and files in the map