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Network Security · Module 2 of 10

Networking for security

Review the networking basics every defender needs.

📖 Key ideas

  1. OSI model has 7 layers; TCP/IP has 4.
  2. IP addresses identify hosts; ports identify services (22 SSH, 80 HTTP, 443 HTTPS).
  3. TCP is connection-oriented (3-way handshake); UDP is connectionless.
  4. DNS translates names to IPs.
  5. Wireshark captures and inspects packets.
💡 Real-life example: Ports are apartment numbers in a building (IP address); each service lives in its own flat.
PortNumber identifying a service
TCP handshakeSYN, SYN-ACK, ACK
DNSDomain Name System
WiresharkPacket analyser