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Cyberbirds Meeting #2

February 28th

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Meeting Outline

  • Introduction of Cybersecurity
  • Networks – Videos 1 & 2
  • OverTheWire

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Networks

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Review (videos 1 & 2)

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What is a host?

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What is a host?

Types of Hosts: Clients/Servers

Host - any device that can send or receive traffic (another word for data)

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Client

Server

Initiates requests

Receives a request and provides a response (serves)

Ex: Web browser requesting a webpage

Ex: Website server providing HTML/other associated files

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  • All hosts follow the same rules of how to communicate to the internet.

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  • Every host follows a certain set of protocols, which we will get to later.

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IP Addresses

10101010010100011111111100000000

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IP Addresses

10101010010100011111111100000000

10101010 01010001 11111111 00000000

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IP Addresses

10101010010100011111111100000000

10101010 01010001 11111111 00000000

​

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170 81 255 0

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IP Addresses

  • IP Address: The number that uniquely identifies each host
  • Every host needs an IP address to communicate on the internet (just like a phone number is needed to call others).

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How IP Addresses are used

Client

Server

101010100101000101010101010101001

When a client sends a request – aka a packet of data — the packet is stamped with a IP Address

Source IP Address: 74:45:226:31

Destination IP Address: 123:21:91:21

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How IP Addresses are used

Client

Server

010010100101010101010110101010

When a server sends a response the packet is still stamped with a IP Address so it can be correctly routed back to the client

Source IP Address: 123:21:91:21

Destination IP Address: 74:45:226:31

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Networks

Network: A logical grouping of hosts that require similar connectivity

  • Any time two hosts are able to communicate, a network has been established.

A line signifies communication

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Networks

Each of these is a network. All are made up with devices containing similar connectivity. Each of the devices communicate with each other.

Networks can contain other networks (subnetting)

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Networks are connected via the internet

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Connecting Hosts Doesn’t Scale…

The amount of connections required increases greatly as hosts are added

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The Solution: Switches

Switch: Device that learns which hosts are connected to certain ports. It then uses that info to facilitate communication within a network

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Home wifi network - example

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Routers

  • Router: Facilitates communication between networks.
  • Routers also provide filtering as a traffic security point.
  • Routers learn which networks they are attached to by storing IP addresses in routing tables
  • Connections of routers make up the internet

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Protocols: DNS

  • Translates human-readable domain names (e.g., example.com) into IP addresses that computers use to identify each other on networks.
  • Operates over UDP (port 53) for fast, connectionless queries and TCP (port 53) for larger or more secure data transfers.

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Protocols: ARP

  • Maps IP addresses to MAC addresses within a local network to enable communication between devices
  • Uses request-reply messages; a device broadcasts an ARP request asking "Who has this IP?" and the corresponding device responds with its MAC address.
    • Creates ARP Tables

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An example of CTF challenge DEMO

(steganography)