Networking & Cybersecurity Essentials

Cheatsheet Content

1. Network Classification Based on Geographical Coverage: PAN (Personal Area Network): Up to 10m (e.g., Bluetooth). LAN (Local Area Network): Building/campus, high speed (e.g., Ethernet/WiFi). MAN (Metropolitan Area Network): Covers a city (e.g., cable TV network). WAN (Wide Area Network): Spans countries/continents (e.g., Internet). Based on Topology: Bus, Star, Ring, Mesh, Tree define connection methods. Based on Architecture: Client-Server Model: Centralized server provides services. Peer-to-Peer Model: Decentralized, all devices share resources equally. 2. Network Topologies Bus Topology All devices connected to a single central cable (bus). Data travels in both directions; terminators prevent signal bounce. Advantages: Simple, inexpensive, easy to extend. Disadvantages: Single point of failure, performance degrades with traffic. [Device1] --- [Device2] --- [Device3] --- [Device4] | | | | (All connected to a single backbone cable) Star Topology All devices connected to a central hub/switch. Data passes through the hub to reach the destination. Advantages: Easy to install/manage, node failure doesn't affect others. Disadvantages: Hub failure disables entire network, requires more cabling. [Hub/Switch] / | \ [Device1][Device2][Device3] 3. CSMA/CD and CSMA/CA CSMA/CD (Carrier Sense Multiple Access with Collision Detection) Used in wired Ethernet (LANs). Process: Carrier Sense: Listen to bus before transmitting. If idle, transmit; if busy, wait. Collision Detection: If devices transmit simultaneously, collision detected. Backoff: Both stop, wait random time, retry. CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) Used in wireless networks (WiFi). Process: Carrier Sense: Listen before transmitting. Send RTS (Request to Send) to AP. AP sends CTS (Clear to Send) if medium free. Then transmit data. Avoids collisions proactively (addresses hidden terminal problem). 4. Network Devices Device Function Layer Repeater Regenerates signals to extend network range. Physical Bridge Connects two LANs; filters/forwards based on MAC address. Data Link Switch Multi-port bridge; forwards data to specific device using MAC address. Data Link Router Connects different networks; routes packets using IP addresses. Network Gateway Connects dissimilar networks; performs protocol translation. All 5. Client-Server vs. Peer-to-Peer Aspect Client-Server Model Peer-to-Peer Model Structure Centralized Decentralized Server Role Dedicated server provides services No dedicated server; all nodes are equal Scalability Limited by server capacity Highly scalable Security Easier to manage and secure Less secure; each peer manages its own security Cost Higher (server hardware/software) Lower (no central server) Example Web browsing, Email BitTorrent, Skype 6. IP Addressing Unique numerical identifier for devices on a network. Purpose: Host identification and location addressing for routing. Versions: IPv4: 32-bit, dotted-decimal (e.g., $192.168.1.1$). Nearly exhausted. IPv6: 128-bit, hexadecimal (e.g., $2001:0db8:85a3::$). Vast address space. Classes (IPv4): A, B, C, D, E for different network sizes. Public vs. Private IPs: Public: Globally routable. Private: Used within LANs ($10.x.x.x$, $192.168.x.x$). Subnet Mask: Separates network and host portions of an IP address. DHCP: Dynamically assigns IP addresses. 7. Internet Application Protocols Protocol Full Form Purpose HTTP/HTTPS HyperText Transfer Protocol (Secure) Web page transfer FTP File Transfer Protocol File upload/download SMTP Simple Mail Transfer Protocol Sending email POP3/IMAP Post Office Protocol / Internet Mail Access Protocol Receiving email DNS Domain Name System Translates domain names to IP addresses TCP Transmission Control Protocol Reliable, connection-oriented data delivery UDP User Datagram Protocol Fast, connectionless delivery VoIP Voice over IP Voice calls over Internet SSH Secure Shell Secure remote login 8. TCP/IP Protocol Suite The TCP/IP model has 4 layers: Application Layer: HTTP, FTP, SMTP, DNS – user applications. Transport Layer: TCP (reliable) and UDP (fast) – end-to-end communication. Internet Layer: IP, ICMP – routing and addressing. Link Layer: Ethernet, WiFi – physical transmission. Application Layer (HTTP, FTP) ↓ Transport Layer (TCP, UDP) ↓ Internet Layer (IP, ICMP) ↓ Link Layer (Ethernet, WiFi) 9. Internet Architecture Hierarchical, layered structure: End Systems (Hosts): User devices (PCs, phones). Access Networks: LANs, WiFi, ISP connections. Core Network: Routers, switches, fiber backbones. ISPs (Internet Service Providers): Connect users to the Internet. IXPs (Internet Exchange Points): Where ISPs interconnect. [User Devices] → [Access Network] → [ISP] → [Internet Core] → [IXP] → [Other ISPs] → [Destination] 10. Common Cyber Attacks Malware: Viruses, worms, Trojans, ransomware. Phishing: Fraudulent emails/websites stealing credentials. DoS/DDoS: Overwhelming a server with traffic. Man-in-the-Middle (MitM): Intercepting communication. SQL Injection: Injecting malicious code into databases. Spyware: Secretly monitors user activity. Social Engineering: Manipulating users to divulge info. Zero-Day Exploits: Attacks on unknown vulnerabilities. 11. System Protection & Cure Firewalls: Filter incoming/outgoing traffic. Antivirus/Antimalware: Detect and remove malicious software. Intrusion Detection/Prevention Systems (IDS/IPS): Monitor and block threats. Encryption (SSL/TLS): Protect data in transit. VPNs: Secure remote access. Regular Updates/Patching: Fix vulnerabilities. User Training: Awareness about phishing/social engineering. Backups: Regular data backups for recovery. 12. Encryption in Networks Converts plaintext to ciphertext using algorithms and keys. Symmetric Encryption: Same key for encryption/decryption (e.g., AES). Asymmetric Encryption: Public key encrypts, private key decrypts (e.g., RSA). Sender → Plaintext → [Encryption Algo + Key] → Ciphertext → Network → [Decryption Algo + Key] → Plaintext → Receiver Used in HTTPS, VPNs, SSH for confidentiality. 13. Cybersecurity & CIA Triad Cybersecurity: Protecting systems, networks, and data from digital attacks. CIA Triad: Confidentiality: Data accessible only to authorized users (Encryption, access controls). Integrity: Protecting data from unauthorized modification (Hashing, digital signatures). Availability: Data/resources accessible when needed (Redundancy, backups, DDoS protection). 14. Basic Information Security Model Comprises assets, threats, vulnerabilities, and controls. [Threats] → [Exploit Vulnerabilities] → [Assets at Risk] ↓ [Security Controls] (Prevent, Detect, Respond) 15. Assets in Information Security Anything of value to an organization: Data: Databases, customer info, intellectual property. Hardware: Servers, PCs, routers, IoT devices. Software: OS, applications, custom code. People: Employees, their skills and knowledge. Reputation: Brand trust, customer confidence. Financial Assets: Money, stocks, transactions. 16. Popular Cybersecurity Threats Malware: Viruses, worms, Trojans, spyware. Phishing/Spear Phishing: Deceptive emails tricking users. Ransomware: Encrypts data, demands ransom. Insider Threats: Malicious or negligent employees. DDoS Attacks: Overload services. Advanced Persistent Threats (APTs): Long-term targeted attacks. IoT Attacks: Compromising smart devices. Zero-Day Exploits: Unknown vulnerabilities. 17. Vulnerabilities & Security Controls Vulnerabilities: Weaknesses that can be exploited (e.g., unpatched software, weak passwords). Security Controls: Safeguards to protect assets. Technical: Firewalls, encryption, IDS. Administrative: Policies, training, audits. Physical: Locks, biometrics, surveillance. 18. Password Best Practices Length & Complexity: 12+ characters, mix upper/lowercase, numbers, symbols. Uniqueness: Different passwords for different accounts. Password Managers: Generate/store strong passwords. Multi-Factor Authentication (MFA): Always enable. Avoid Common Words: Don’t use simple words or personal info. Change Periodically: Especially after breaches. Don’t Share or Write Down: Keep passwords private. Monitor for Breaches: Use tools like HaveIBeenPwned. 19. Cybersecurity Teams Red Team: Ethical hackers simulating attacks. Blue Team: Defenders monitoring, detecting, and responding to threats. Purple Team: Collaboration between Red and Blue for improved defense. SOC (Security Operations Center): 24/7 monitoring and incident response. Forensics Team: Investigates breaches, collects evidence. GRC Team: Governance, Risk, Compliance – ensures policies are followed. 20. Digital Content Ownership Rules Copyright: Protects original works; requires permission for use. Open Source Licensing: Allows use/modification under specific terms (e.g., GPL, MIT). Public Domain: Works not protected by copyright; free to use. Fair Use: Limited use of copyrighted material without permission (e.g., education, criticism). Plagiarism & Piracy Prevention: Ethical/legal rules against copying/distributing without consent. 21. Social Media & Online Impact Social Media Addiction: Leads to anxiety, depression, sleep loss, reduced productivity. Political Impact: Enables misinformation, election interference, echo chambers, digital authoritarianism. Online Tracking: Companies collect browsing data for targeted ads; invades privacy, risks data misuse. Breach of Online Privacy: Identity theft, financial loss, blackmail, loss of personal autonomy.