Notes, summaries, assignments, exams, and problems for Computers

CIA Triad

The CIA Triad consists of Confidentiality, Integrity, and Availability. Related concepts include Authentication, Accountability, and Auditability.

Types of Harm

• Interception
• Interruption
• Modification
• Fabrication

Web Technologies

HTML

• GET: Embeds parameters into the URL.
• POST: Sends data directly to the server; more secure.

PHP

• PUT: Used to create or replace a file at the specified URL. Sends data like POST, more suitable for uploading files.

Penetration Testing

5 Steps to Penetration Testing:

1. Reconnaissance
2. Scanning
3. Gaining Access
4. Maintaining Access
5. Clearing Tracks

Security Controls

• Prevention: Outright stopping an attack.
• Deterrence: Making an attack harder.
• Deflection: Making a target less attractive.
• Mitigation: Lessening the harm.
• Detection: Identifying

Smith & Mosier Design Categories

The following categories represent the Smith & Mosier standards for interface design:

• Data Entry (199): User actions involving input of data to a computer and computer responses to such inputs.
• Data Display (298): Computer output of data to a user and assimilation of information from such outputs. Note: Data should be displayed in a usable form; do not force users to convert displayed data.
• Sequence Control (184): User actions and computer logic that initiate, interrupt, or terminate transactions.
• User Guidance (110): Error messages, alarms, prompts, labels, and formal instructional material to assist user interaction.
• Data Transmission (83): Computer-mediated communication among system users and other systems.

NETWORKING

1- Characteristics of Electronic Cables

Impedance, attenuation, and capacitance are crucial in electronic cables.

Impedance:

Resistance to electron movement in an AC circuit, measured in ohms (Ω).

Attenuation:

Resistance to electron flow, measured in db/m.

Capacitance:

Energy storage in a cable, measured in picofarads (pF).

2- Physical Description of Cables

Twisted Pair: Protects against crosstalk and noise.

Coaxial Cable: Consists of copper conductor, plastic insulation, and shielding.

Fiber-Optic Cable: Core, cladding, buffer, strengthening material, and outer jacket.

3- UTP vs. STP

Shielding reduces electrical noise in STP but makes installation complex.

4- Crimping RJ-45 UTP Cables

Creates straight-through and crossover cables for connecting... Continue reading "Understanding Networking: Cables, Protocols, and Topologies" »

Java Programming Fundamentals

This document provides a quick reference to fundamental Java programming concepts, including object-oriented programming basics, common data structures like ArrayLists, handling user input, string manipulation, type conversion, and file input/output operations.

Object-Oriented Programming: The Persona Class

Below is a basic definition of a Persona class, illustrating fields and a constructor. In a complete implementation, you would also include getter and setter methods for each field.

public class Persona {
    private String nombre;
    private int ojos;
    private int piernas; // Added for completeness based on constructor
    private int brazos; // Added for completeness based on constructor

    public Persona(

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Athens Dublin Istanbul Lisbon London Oslo Paris... Continue reading "Customer Feedback and Catalog Request Form" »

Tree Traversal Methods

Preorder traversal: Visit the root, visit the left subtree, and then visit the right subtree.

Inorder traversal: Visit the left subtree, visit the root, and then visit the right subtree.

Postorder traversal: Visit the left subtree, visit the right subtree, and then visit the root.

Breadth-First Traversal: Visit the root, visit the children of the root (left to right), and then the children of the children (left to right), going down level by level.

Depth-First Traversal: Rather than visiting the tree level-by-level like in breadth-first traversal, visit the root, go all the way down the left on one path, and then move across the tree to the right, going down all the paths until the end.

Hashing and Collision Resolution

Hashing:

Functions and Arguments

A function is a module of program code that takes input (arguments) and produces output (a return value).

• Arguments allow us to customize the operation performed by the function.
• The return value is often the result of executing the code.
• Calling a function causes the code in a function to execute. If called again, it will execute again.

To document a function, use a multi-line comment immediately after the def line.

Local Variables

Local variables are variables used inside functions.

• They are accessible/usable within that function only.
• This refers to the variable's scope.

Global Variables

Global variables are variables used outside of a function.

• Global variables' scope includes both inside and outside of functions.
• However, since

Wide Area Networks

Applications utilize application-level protocols (such as MQTT, CoAP, HTTP, and WS) to communicate effectively across networks.

MQTT: Publish/Subscribe Messaging

MQTT is a lightweight messaging protocol based on TCP/IP. It utilizes Quality of Service (QoS) levels to manage delivery:

• QoS 0 (At Most Once): Messages are sent with no guarantee of arrival.
• QoS 1 (At Least Once): Subscribers acknowledge message reception. The broker stores the message and retries until an acknowledgment is received.
• QoS 2 (Exactly Once): The most reliable delivery method. The broker ensures messages are delivered to subscribers without duplicates.

MQTT Security

MQTT does not provide native security. It can utilize TLS/SSL encryption for data in transit,... Continue reading "MQTT vs CoAP: IoT Communication Protocols Explained" »

Understanding Computer Security

Common Threats

• Worm: Designed to replicate itself, a worm operates as a standalone application, unlike a virus.
• Trojan: Disguised as a legitimate program (e.g., a screensaver), a Trojan operates covertly to inflict damage.
• Phishing: Attackers impersonate trustworthy entities to steal sensitive information, exploiting social engineering tactics.

Network and Security Concepts

• Simple Mail Transfer Protocol (SMTP): A standard for email communication, SMTP is known for its lack of robust security.
• Sandboxes: Software environments that isolate programs to prevent them from harming the host system, commonly used in web browsers.

Wireless Security

• Wireless Internet (Wi-Fi): Enables wireless communication between devices, forming

Network Classification by Device Roles

Networks can be classified based on the roles of the devices within them:

• Client-Server: This is the most common type. A powerful server provides services to multiple clients and is always available. Example: A web server.
• Peer-to-Peer: In this model, all computers have equal roles and share resources directly. Example: BitTorrent.

Router Functions in Home Networks

Routers provided by Internet Service Providers (ISPs) often integrate the functions of multiple devices, including:

• Hub
• Modem
• Access Point

MAC Address Translation

The MAC address 08-2E-5F-14-93-A0 in decimal is 8-46-95-20-147-160.

Switches and the OSI Model

Switches operate at Level 2 (Data Link Layer) of the OSI model. Other devices that work at this level... Continue reading "Network Types, MAC Addresses, and OSI Model Explained" »