Internet & More

Question 1

MAC

Answer 1

Media Access Control address
48-bit number written in hexadecimal, with bytes separated by colons (08:00:27:3b:8f:ed)
Always remains the same for a device!

Question 2

NIC

Answer 2

Network Interface Card

- In PCs and Laptops, to connect to WiFi routers

Question 3

Ipv4

Answer 3

32 bit number, 4 8-bit numbers

Question 4

CIDR

Answer 4

Classless inter-domain routing
128.143.1.1/16 -> means machines share the same upper 16 bits
E.g. All addresses are in form: 128.143.xxx.xxx

Question 5

DSLAM

Answer 5

Digital Subscriber Line Access Multiplexer
- Allows internet signals to be sent over cable TV wires
( why you can connect both TV and router to same cable socket)

Question 6

Path of Web Requests

Answer 6

Web request -> laptop NIC -> Wifi router -> DSLAM -> ISP routers -> … Router -> Machine by MAC Address
(Once the packet is at the lowest level of the hierarchy (no more routers), the final router uses the MAC address to determine final destination)

Question 7

LAN

Answer 7

Local Area Network - lowest level because all machines there are connected through a single router

Question 8

ARP

Answer 8

Address Resolution Protocol

• Router needs to know the MAC address of a machine with a given local IP address
• Stores map of IP -> MAC addresses

Question 9

Lowest IP Address on a LAN

Answer 9

Normally the router!

Question 10

CAM

Answer 10

Content Addressable Memory

• Memory hardware used in routers and switches
• Map MAC addresses to corresponding ports
• If CAM is full, will broadcast message on all ports
• This is an attack vector, by sending packets w/ random MAC addresses to the switch

Question 11

Ports

Answer 11

On a network, a port is a communication endpoint

• At the software level, within an operating system, a port is a logical construct that identifies a specific process
• Allow a process to communicate over a network
• Allows multiple processes to communicate with network at same time
• 16 bit number (1 - 2**16-1) (65535 ports)

Question 12

Open port

Answer 12

A port that accepts a connection from an external process

Question 13

5 Layer Internet Protocol Model

Kurose, Forouzan

Answer 13

Application Layer
Transport Layer (TCP/UDP)
Network Layer (IP)
Data Link Layer (MAC)
Physical Layer

Question 14

OSI Model

Answer 14

(7 layers)
Application
Presentation
Session
Transport
Network
Data Link
Physical

Question 15

P2P

Answer 15

Peer-to-Peer

Clients exchange information directly with each other (as opposed to client-server model)

Question 16

Client-server model

Answer 16

Client initiates communication with a waiting server, which responds

Question 17

SSH

Answer 17

Secure Shell

Question 18

NAT

Answer 18

Network Address Translation

Question 19

Why do we use “models” of the internet stack?

Answer 19

So we can model each layer in terms of encapsulation ->

• Each layer is independent, managing the communications within that layer only
• Each layer doesn’t care about other layer actions

Question 20

Application Layer (5 layer model)

Answer 20

Layer 5 - Communicate between applications

• Protocols
  
  • HTTP
  • FTP
  • BitTorrent
  • SMTP

Question 21

Transport Layer (5 layer model)

Answer 21

Layer 4 - Communication of processes over internet

• TCP (transmission control protocol) - guarantees packet get to destination
• UDP (user datagram protocol) - no guarantees, simpler

Question 22

Network Layer (5 layer model)

Answer 22

Layer 3 - How packets flow between routers
- Implements IP (Internet Protocol)
(traceroute can show this path_
Uses ICMP - Internet Control Message Protocol

Question 23

ICMP

Answer 23

Internet Control Message Protocol

Question 24

Data Link Layer (5 layer Model)

Answer 24

Layer 2 - communications between NICs (Network Interface Cards)
- Implements MAC protocol

Question 25

Physical Layer (5 layer model)

Answer 25

Layer 1

Convert 1-0s into transmittable form (light, radio, electrical, sound)

Question 26

Socket

Answer 26

An API that allows programs to communicate over a network

2 main types
- TCP
- UDP
others, including SOCK_RAW, and ICMP

Question 27

DDOS

Answer 27

Distributed Denial of Service Attack

- Overwhelm a web server with traffic, causing it to become temporarily unavailable

Question 28

CNC (C2)

Answer 28

Command and Control

Question 29

HTTPS port

Answer 29

443

Question 30

HTTP Default port

Answer 30

80

Question 31

SSH Port

Answer 31

22

Question 32

Telnet

Answer 32

“Teletype Over Network”

Telnet server listens on port 23

Question 33

Static content

Answer 33

Files served “as-is” (HTML docs, CSS, JS, images, video, fonts)

Question 34

Dynamic Content

Answer 34

Files update before being served to a client

Question 35

Ransomware

Answer 35

Malicious code that “holds a machine hostage” by encrypting its files.
- Generally demand money in exchange for decrypting the files

Question 36

Plaintext

Answer 36

Original text/data before encryption is applied

Question 37

Caesar Cipher

Answer 37

One of the earliest encryption algorithms

• Replaces each letter with another a fixed number of positions away in the alphabet (an example of a substitution cipher)
• ROT13 (replace letters with the letter 13 away) can be used the for both encryption and decryption, providing very little security

Question 38

ASCII

Answer 38

American Standard Code for Information Interchange

Question 39

IPC

Answer 39

Inter-process Communication