WEEKLY RECAP

Encryption & Caesar Cipher

• Encryption: Process of converting readable data (plaintext) into unreadable data (ciphertext) using algorithms.
• Caesar Cipher: A substitution cipher where each letter is shifted by a fixed number of positions in the alphabet.
  • Example: Shift = 3 → A → D, B → E.
• Python Code: Implemented Caesar Cipher with encryption and decryption functions.

Linux Commands (grep, find, wc)

• grep: Searches for patterns in files.
  • Example: grep "error" logfile.txt → finds “error” in file.
• find: Locates files and directories.
  • Example: find /home -name "*.txt" → finds all .txt files.
• wc (word count): Counts lines, words, and characters.
  • Example: wc -l file.txt → gives number of lines.

Firewall vs Antivirus

• Firewall: Acts as a barrier between trusted and untrusted networks. Monitors and blocks suspicious traffic.
• Antivirus: Detects and removes malware from a system. Focuses on files/programs rather than traffic.
• Key Difference: Firewall = network protection, Antivirus = endpoint protection.

First Challenge on TryHackMe (Pre-Security Path)

• Explored Pre-Security Path basics.
• Learned about networking, security concepts, and beginner CTF-style exercises.
• Documented experience with screenshots to track progress and understanding.

Subnet Mask & Default Gateway

• Subnet Mask: Divides an IP address into network ID and host ID. Defines which part of the address belongs to the network.
  • Example: 255.255.255.0 → 24 bits for network, 8 bits for hosts.
• Default Gateway: Router IP that connects a local network to external networks (e.g., the internet).
• Together: Subnet mask = internal organization, Gateway = external communication.

WannaCry Ransomware Case Study (2017)

• Spread: Exploited Windows SMB vulnerability (EternalBlue).
• Self-propagating worm: Spread without user interaction.
• Impact: Hit 230,000+ computers in 150+ countries. Victims included NHS, FedEx, Renault.
• Mitigation: Kill switch accidentally discovered by researcher slowed spread.
• Lesson: Importance of patching, backups, and cybersecurity readiness.