Networks & Security Notes PDF

Final Exam Notes Networks & Security Section Decimal (Base 10) 10 Options (0-9) if a Number is written as 6510 , indicates that its a decimal How Many Options Does X Decimal Digit Cells Produce? Rule = 10n n = Number of Cells Binary (Base 2) 2 Options (0-1) if a Number i...

Final Exam Notes Networks & Security Section Decimal (Base 10) 10 Options (0-9) if a Number is written as 6510 , indicates that its a decimal How Many Options Does X Decimal Digit Cells Produce? Rule = 10n n = Number of Cells Binary (Base 2) 2 Options (0-1) if a Number is written as 1101102 , indicates that its a decimal How Many Options Does X Binary Digit Cells Produce? Rule = 2 n n = Number of Cells Hexa (Base 16) 1 Hexa = 4 bits 0,1, 2, 3, 4, 5, 6, 7, 8, 9 10 = A 11 = B 12 = C 13 = D 14 = E 15 = F How To Convert Decimal to Binary: 47 Binary to Decimal: 101111 128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1 0 0 1 0 1 1 1 1 0 0 1 0 1 1 1 1 32+8+4+2+1 = 47 4710 = 0 0 1 0 1 1 1 1 2 4710 = 0 0 1 0 1 1 1 1 2 Hexa to Binary: 4A Hexa to Binary: 1001010 4 A 8 4 2 1 8 4 2 1 8 4 2 1 8 4 2 1 0 1 0 0 1 0 1 0 0 1 0 0 1 0 1 0 4 8+2 = 10 (A) 4A 16 = 0 1 0 0 1 0 1 0 2 4A 16 = 0 1 0 0 1 0 1 0 2 Hexa to Decimal: A7 Hexa to Decimal: 42 A 7 42 / 16 = 2.625 16 1 16 * 2 = 32 42-32 = 10 10 * 16 = 160 + 42 10 = 2A 16 7*1=7 160+7 = 167 A7 16 = 167 10 Download Time (seconds) = Size (kilobits) / Bandwidth (kilobit per second) Upload Time (seconds) = (Size (kilobits) / Bandwidth (kilobit per second)) ÷ 4 Size Conversions MEGA TO KILO = x 1,000 GIGA TO KILO = x 1,000,000 BYTE TO BIT = x 8 IP Address IP is 32 bits divided into four 8 bits, ranging from 0 to 255 8 bits 8 bits 8 bits 8 bits Size of Business IP Address Small Network. Network. Network. Host Medium Network. Network. Host. Host Large Network. Host. Host. Host Submit Mask Identifies if its a Network or a Host If Network 255 and if 0 then Host Example: 200.200.200.0 / 24 Determine Answers Subnet Number (Submit Mask) Subnet Number (Submit Mask) : 255.255.255.0 Network ID Network ID: 200.200.200.0 First Host First Host: 200.200.200.1 Last Host Last Host: 200.200.200.254 Broadcast Address Broadcast Address: 200.200.200.255 Crossover Straight Through TX 1. White Green TX 1. White Orange TX 1. White Orange RX 1. White Orange TX 2. Green TX 2. Orange TX 2. Orange RX 2. Orange RX 3. White Orange RX 3. White Green RX 3. White Green TX 3. White Green 4. Blue 4. Blue 4. Blue 4. Blue 5. White Blue 5. White Blue 5. White Blue 5. White Blue RX 6. Orange RX 6. Green RX 6. Green TX 6. Green 7.White Brown 7.White Brown 7.White Brown 7.White Brown 8. Brown 8. Brown 8. Brown 8. Brown Switch & Hub Write down each PC bandwidth. Assume that we replaced the switch with a hub , Write down each PC bandwidth. Using a Switch: Each PC has 100 Mbps. Replacing Switch With a Hub: Each PC has 25 Mbps Write down each PC bandwidth. Each PC has 25 Mbps Chapter 1 OSI Model Open System Internetworking OSI is a Standardization For OSI to be standardized, Layers were created which is equal to the process. These layers have a name & number. These names & numbers are standard. "hi" 7. Application Layer jpeg,mp3, Ascii 6. Presentation Layer Session ID 5. Session Layer Error Correct 4. Transport Layer IP Detection 3. Network Layer Error Detection 2. Data Link Layer bits (0 &1) 1. Physical Layer Protocols Data Unit (PDU) Ascii “hi” Session ID 7. Application Layer It’s responsible of the data coming out of your program. 6. Presentation Layer It’s responsible on how the data is being presented. 5. Session Layer It talks about the session ID and what it has to do with an operating system. Each OS has a Different Session ID 4. Transport Layer It’s responsible for end-end delivery over a network & Error Correction. Header Destination Port Source Port.... PDU This is Known as Segment 16 bit 16 bit 32 bit The Transport Layer Protocols Protocols Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Reliability Reliable Unreliable Connection Protocol Connection-Oriented Connectionless TCP/IP Network to make a connection Used For Real-Time Apps between The Server & The Client TCP includes a Three-way-handshake Synchronization (32 bit) Acknowledgment User Server Synchronization (32 bit) Acknowledgment 3. Network Layer Header Destination IP Source IP.... Segment This is Known as Packet 32 bit 32 bit 64 bit 32 2 = 4G (4 Billion) of Different IP Address. 2. Data Link Layer It is responsible for transporting data within a network & Error Detection Header Tail Destination MAC Source MAC.... Packet CRC This is Known as Frame 48 bit 48 bit 96 bit Media Access Control MAC is burned on the card it doesn't change (its unique from factory) Cyclic Redundancy Check CRC checks if here's en error or not, sender counts hm 15 / 0s there are and States it so the sender knows. 1. Physical Layer It’s responsible for the way of sending the binary numbers (0s &1s). Those (0s &1s) can be sent wireless or wired (Like Fiber Optics or Copper Cables) Incapsulation & Decapsulation I’m Sending: From Layer 7 To Layer 1 = Incapsulation I’m Receiving: From Layer 1 To Layer 7 = Decapsulation Chapter 2 Cables, Wi-Fi & Devices Cables Cables that we connect to the devices are known as Network Cables Cables Work on the Physical Layer Twisted Pair Cable (Cooper) Consists of 2 or 4 pairs of copper wires in a plastic cover it can be shielded (STP) or unshielded (UTP) These Cables Can Only Travel a max Distance of 100m The cable has signals of 0s & 1s and those are based on voltages. Anything above the threshold of 3.3 volts is considered a 1 Beyond 100m the signal will go below 3.3 volts. Fiber Optics Fiber Optics uses light to transmit signal Single Mode Fiber Single Mode Fiber consist of a very small glass core allowing only a Single ray of light to travel across This greatly reduces the dispersion of light signal supporting high Bandwidth over a very long distance This process is Known as Total Reflective because it reflects the entire Signal Wirelessly Fidelity (WI-FI) We Need Wi-Fi to Have a Larger Bandwidth & Longer Distances Wi-Fi Has Several Protocols WI-FI Protocols NAME IEEE CODE YEAR FREQUENCY BANDWIDTH Wi-Fi 1 802.11b 1999 2.4 GHz 11 Mbps Wi-Fi 2 802.11a 1999 5 GHz 54 Mbps Wi-Fi 3 802.11g 2003 2.4 GHz 54 Mbps Wi-Fi 4 802.11n 2009 2.4/5 GHz 600 Mbps Wi-Fi 5 802.11ac 2014 2.4/5 GHz 2.3 Gbps Wi-Fi 6 802.11ax 2019 2.4/5 GHz 9.6 Gbps Why WI-FI 2 Was Unpopular? Because The Chips Were Expensive to Produce so They Returned To The 2.4 GHz Chips In Wi-Fi 3 but Since Wi-Fi 4 They Use Dual Chips (2.4 & 5 GHz) Devices Hub A hub is a device that connects multiple computers or devices in a network. When one device sends data to the hub, it forwards that data to all the other connected devices but the PC checks the MAC address & declines if not for them. Cons Pros Bad Security (Doesn’t Read MAC address) Cheap Bandwidth is Divided Regenerates signal over distance Collusions & CSMA/CD If PC3 & PC1 are sending a message at the same time a clash will occur known as Collusion So a protocol was created to create a solution known as the Carrier Sense Multiple Access/ Collusion Detection (CSMA/CD) CSMA/CD Stop All Devices From Sending Anything & a Random Nanosecond Timer is Set For Each Device No Data Should be Sent Until The Timer Reaches 0, When 2 Devices Reach 0 The Timer Resets & Randomized Again Switch Each port in a switch has full bandwidth. All ports can transmit data simultaneously without collisions. Switches enhance security and maintain bandwidth compared to hubs. A switch acts as a relay, controlling communication between devices. Chapter 3 Network Security Security Goals Technical Goals CIA Concept Goals Confidentiality Prevent unauthorized data access. Integrity Protect data consistency and detect changes. Availability Ensure resources remain accessible to legitimate users. AAA Concept Goals Authentication Verifies identity (e.g., passwords). Authorization Regulates access to resources. Accounting Tracks activities and identifies responsible entities. Chapter 4 Common Attacks Terminologies Terminology Description Hacker Learns system details to extend capabilities. Cracker Uses hacking skills for malicious purposes. Ethical Hacker Security professionals using hacking defensively. Black Hats Malicious hackers focused on destructive activities. White Hats Defensive hackers, also known as security analysts. Gray Hats Operate both offensively and defensively. Malicious Hacker's Five Phases Phases Phase Name Description 1 Reconnaissance Gathering information using active or passive methods 2 Scanning Using data from reconnaissance to identify vulnerabilities. 3 Gaining Access Exploiting vulnerabilities 4 Maintaining Access Ensuring persistent control through backdoors, rootkits, or trojans. 5 Covering Tracks Concealing activities to avoid detection and legal action. Types of Security Threats Security Threat Description Interruption Denial of access to system assets. Interception Unauthorized access to system assets. Modification Unauthorized tampering with data or resources. Fabrication Insertion of fake objects or data into the system. Attack Techniques Technique Description Overwhelms system resources, rendering them unusable. Denial of Service (DoS) Targets memory, processor cycles, and bandwidth. Distributed DoS (DDoS) Uses multiple systems (zombies) to flood a target. Man-in-the-Middle (MITM) Intercepts communication between two parties. Brute Force Attack Automated guessing of credentials or cryptographic keys. Malware Threat Description Self-replicating code that propagates and executes a payload (e.g., data corruption). Viruses Phases: Dormant, propagation, and triggering phases. Email Viruses Spread via attachments or embedded scripts Trojan Horse Malicious programs disguised as legitimate ones, often installing backdoors. Worms Network-spreading malware that exploits vulnerabilities. Logic Bombs Embedded code that activates under specific conditions (e.g., time or event). Backdoors Secret entry points bypassing security mechanisms. Zombies Infected computers used to launch further attacks, especially DDoS. Countermeasures 1. Prevention 2. Detection 3. Identification 4. Removal Chapter 5 Cryptography Introduction to Cryptography The science of secret writing, enabling secure communication. Encryption (Ciphering) Converts plaintext into unreadable ciphertext. Decryption (Deciphering) Reverts ciphertext back to plaintext by authorized individuals. Cryptoanalysis The study of breaking cryptographic methods to reveal secrets by unauthorized entities. Types of Cryptographic Systems Type Description Uses a single secret key for encryption and decryption. Symmetric Key Cryptosystems Requires secure distribution of the key, which can be challenging. Employs a key pair: public key (for encryption) and private key (for decryption). Asymmetric (Public Key) Cryptosystems Public keys are shared openly, while private keys remain confidential. Hybrid Cryptosystems Combines symmetric and asymmetric cryptography to balance security and efficiency. Symmetric Cryptography Details Encryption Types Ciphers Description Substitution Replace letters with others (e.g., Caesar Cipher, One-Time Pad). Transposition Rearrange text order (e.g., Column Transposition Cipher). Product Combine substitution and transposition (e.g., DES, AES). Examples Examples Description Caesar Cipher Shifts characters by a fixed number of positions. OTP Ultimate secure cipher using a unique key as long as the message. Advantages Disadvantages Fast Challenges in Key Generation Ensures Secrecy Secure Distribution. Authenticity Non-Repudiation. Asymmetric Cryptography Details Mechanism Public keys encrypt data, and private keys decrypt it. Computationally infeasible to derive private keys from public ones. Advantages Solves key distribution problems with fewer keys required. Disadvantages Slower processing speeds compared to symmetric cryptography. Hybrid Cryptosystems Mechanism Uses public keys for secure key exchange and symmetric keys for message encryption. Advantages Resolves key generation and management issues. Offers better performance than public-key-only systems. Disadvantages Does not inherently guarantee message integrity. Examples of Cryptographic Ciphers Cipher Type Mechanism Strengths Weaknesses Caesar Vulnerable to brute force attacks and Shifts each letter by a fixed number based on a key. Simple and easy to implement. Cipher frequency analysis. Simple Maps plaintext letters to cipher letters using a single Slightly more secure than Caesar Susceptible to frequency analysis. Substitution substitution rule. Cipher. Polyalphabeti Uses multiple substitution alphabets based on a Reduces effectiveness of single-letter Vulnerable to cryptanalysis for longer c Cipher repeating key. analysis. texts. Column Arranges plaintext in a grid and reads it column-wise Vulnerable if the column order or grid Scrambles plaintext efficiently. Transposition based on a specified order. size is known. DES (Data Widely used in secure systems Now considered insecure due to Encryption Combines substitution and transposition for encryption. historically. shorter key length. Standard)