W3 CyberSecurity Flashcards
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OSI: Layer 7
The Application Layer.
Where humans process data and information.
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OSI: Layer 6
The Presentation Layer.
Ensures data is in a usable format.
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OSI: Layer 5
The Session Layer.
Capable of maintaining connections.
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OSI: Layer 4
The Transport Layer.
Data is forwarded to a service capable of handling requests.
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OSI: Layer 3
The Network Layer.
Responsible for which path packets should travel on a network.
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OSI: Layer 2
The Data Link Layer.
Responsible for which physical devices packets should go to.
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OSI: Layer 1
The Physical Layer.
The pysical infrastructure to transport data.
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Layer 7, 6, and 5 are typically implemented how?
Through software.
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Layers 3, 2, and 1 are typically implemented how?
Through hardware.
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Layer 4 is implemented how?
Layer 4 acts as the bridge between software and hardware.
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SDN
SDN, Software Defined Networking, allows more layers of the hardware to be implemented via software.
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HTTP
Hypertext Transfer Protocol
A layer 7 protocol that allows web access.
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FTP
File Transfer Protocol
A layer 7 protocol which allows users to transfer files.
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SNMP
Simple Network Management Protocol
A layer 7 protocol used to read and update network device configurations.
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Application Layer
Layer 7
The business logic and functionality of the application lies here. This is what the users use to interact with services across a network. Most developers create applications on the Application Layer.
Most of the applications you use are on the Application Layer, with the complexity of the other layers hidden.
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Presentation Layer
Layer 6
Typically an unseen layer, but is responsible of adapting, transforming and translating data. This is to ensure the application and layers beneath can understand one another.
Encoding Schemes used to represent text and data, for example ASCII(American Standard Code for Information Interchange) and UTF(Unicode Transformation Format).
Encryption for services, for example SSL (“Secure Sockets Layer”) and TLS (“Transport Security Layer”)
Compression, for example GZip in use in many implementations of HTTP.
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Session Layer
Layer 5
This layer’s responsibility is handling connections between the application and the layers below. It involves establishing, maintaining and terminating connections, otherwise referred to as sessions.
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Common protocols which represent the Session Layer well are:
- SOCKS - A protocol for sending packets through a proxy server.
- NetBIOS - An older Windows protocol for establishing sessions and resolving names.
- SIP (“Session Initiation Protocol”) - For engaging in VOIP (“Voice Over IP”) communications
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Transport
Layer 4
The layer which allows applications to be represented on the network.
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Some well known applications on layer 4:
- TCP (“Transmission Control Protocol”) - Used for many applications, ensuring stability, control of how much data can be sent at any given time, reliability and more.
- UDP (“User Datagram Protocol”) - Lightweight and quick protocol use for many services.
- QUIC (“Quick UDP Internet Connections”) - A protocol designed for faster connections and goes hand-in-hand with the version 2 of the HTTP protocol.
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Network
Layer 3
A layer responsible of routing packets between networks via routers.
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On the network layer, the following protocols reside:
- IP (“Internet Protocol”) - Used everyday when accessing the Internet. Comes in two versions, IP version 4 and 6.
- ICMP (“Internet Control Message Protocol”) - Used by network devices and network operators, to diagnose network connections or for devices to send and respond to error conditions and more.
- IPSec (“Internet Protocol Security”) - Allows encrypted and secure connections between two network devices.
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Data Link
Layer 2
Link networks, as the name implies, consist of protocols designed to send packets through the actual links (physical connections) that network nodes are connected to. A simpler way of thinking of it is that the Link Layer is responsible for moving data from physical over to logical (to the network layer).
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Protocols on the data link layer include:
- Ethernet - An essential protocol used by most operating systems when connecting to networks using a physical cable.
- Wi-Fi (“Wireless Fidelity”) - For accessing networks via radio signals. It uses a family of protocols called IEEE 802.11.xx
- NDP (“Neighbor Discovery Protocol”) - IP version 6(IPv6) uses this protocol on the Link Layer to gather information required to communicate via IPv6
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Physical
Layer 1
Physical layer represents the signaling which allows bits and bytes to transfer between a physical medium. It can be transferred via radio or signals over a cable, using electrical signals or light, for example fiber.
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Examples of the Physical Layer protocols includes:
- CAN Bus (“Controller Area Network”) - Used in microcontrollers and other devices to communicate to other similar devices, not involving a computer. Often used in ICS (“Industrial Control Systems”).
- Ethernet Physical Layer - Used by Ethernet on the physical layer to send signals with speeds up to many gigabits of traffic per second.
- Bluetooth Physical Layer - Bluetooth also has its own specifications on how radio signals should be sent and received.
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IP
Internet Protocol
Allows communication across networks. It exists in two versions IPv4 and IPv6.
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netmask
Dictates how large a network is and which packet is routed within the ntwork and which should be routed outside of the network.
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broadcasting
sending data to everyone on the network.
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broadcast address
is always the last IP address in the network.
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what is the windows command to check ip address?
ipconfig
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what is the linux/mac command to show ip address
ifconfig
or
ip addr show
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NAT
Network Address Translation
Allows a system accepting connections on a public IP to map requests to an internal RFC 1918 IP or vice versa. These are typically firewalls or routers.
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RFC 1918 IPs
IP addresses that are reserved for certain kinds of traffic.
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IPv6
128 bits broken into 8 groups of 4 hex numbers.