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Advanced Networks Flashcards

1
Q

Modulation

A

The encoding of data in a radio wave

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2
Q

Carrier Signal

A

The basis upon which information is superimposed allowing for transmission of data

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3
Q

AM

A

Amplitude Modulation

Varies the amplitude of a carrier signal to encode the message signal

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4
Q

ASK

A

Amplitude Shift Keying

Toggles the amplitude of the carrier signal depending on the message signal

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5
Q

FSK

A

Frequency Shift Keying

Toggles the frequency of the carrier signal between two distinct values depending on the message signal (0 or 1)

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6
Q

PSK

A

Phase Shift Keying

Toggles the phase of a carrier signal depending on the digital signal

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7
Q

Binary PSK

A

Toggles the phase between two states to encode 1 bit (2 states)

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8
Q

Quadrature PSK

A

Toggles the phase between four states to encode 2 bits (4 states)

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9
Q

Eight-PSK

A

Toggles the phase between eight states to encode 3 bits (8 states)

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10
Q

QAM

A

Quadrature Amplitude Modulation

Varies both the phase and amplitude of the to improve bandwidth efficiency

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11
Q

FDMA

A

Frequency Division Multiple Access

Divides a band into channels and assigns each user a channel

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12
Q

(Dynamic) TDMA

A

Time Division Multiple Access

Divides time into slots and allocates each user a time slot

Guard Periods may help space out time slots

Dynamic TDMA considers user requirements and allocates multiple time slots if necessary

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13
Q

CDMA

A

Code Division Multiple Access

Uses orthogonal modulation codes to allow multiple transmissions over the same frequency bands

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14
Q

802.11

A

Wi-Fi

Specifications for PHY Layer and MAC Layer for Wireless Local Area Networks (WLAN)

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15
Q

DSSS

A

Direct Sequence Spread Spectrum

Wi-Fi Modulation Technique

Spreads signal across an entire allocated frequency by modulating with a spreading code (known only to the sender and receiver) at a higher bit-rate
A higher bit-rate (spreading ratio) uses more frequency and improves interference immunity

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16
Q

FDM

A

Frequency Division Multiplexing

Wi-Fi Modulation Technique

Combines multiple signals into one signal for transmission over a single channel
Guard bands between each signal avoid overlap

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17
Q

OFDM

A

Orthogonal FDM

Wi-Fi Modulation Technique

Sub-carrier frequencies are orthogonal with the peak coinciding with the nulls of adjacent subcarriers
Saves bandwidth, allowing for higher data rate but is more susceptible to noise

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18
Q

OFDMA

A

OFDM With Multiple Access

Wi-Fi Modulation Technique

Not every packet utilises the entire bandwidth of a sub-carrier. So sub-carriers (and time allocations) are divided amongst users
Improves efficiency

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19
Q

Beamforming

A

Wi-Fi Spatial Performance Improvement

Focuses radio waves in the direction of a specific client
Improves medium range communications (Provides no benefit for long range and is not needed for short range)

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20
Q

MIMO

A

Multiple-Input Multiple-Output

Wi-Fi Spatial Performance Improvement

Uses multiple antennas at both the transmitter and receiver for simultaneous transmission and reception of multiple data streams

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21
Q

MU-MIMO

A

Multi-User MIMO

Wi-Fi Spatial Performance Improvement

Enables parallel communication with multiple clients

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22
Q

CSMA/CD

A

Carrier Sense Multiple Access/Collision Detection

Ethernet Multiple Access Technique

Detects collisions and retransmits

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23
Q

CSMA/CA

A

Carrier Sense Multiple Access/Collision Avoidance

Wi-Fi Multiple Access Technique

Avoid collisions by checking if a channel is clear before transmitting
Transmitter sends RTS (Ready to Send) message to Receiver
Receiver responds with CTS (Clear to Send) message to Transmitter
Nodes that hear CTS don’t transmit until data is sent

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24
Q

5GHz Wi-Fi

A

More bandwidth but worse penetration than 2.4GHz
Interferes with radar, requiring Dynamic Frequency Selection (DFS)

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25
Q

DFS

A

Dynamic Frequency Selection

Avoids interference with radar by checking if it is detected on a channel and avoiding it if necessary
In-use channels are monitored and channel is changed if radar detected

Adds cost and complexity and is susceptible to false triggers

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26
Q

802.11ax

A

Wi-Fi 6
Designed for efficiency in dense environments
Uses 1024-QAM
Uses 2.4GHz, 5GHz and provisionally 6GHz

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27
Q

TWT

A

Target Wake Time

Allows clients to schedule times with Wi-Fi access points for waking up and sending data
Ideal for IoT and Sensor Networks

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28
Q

LPWAN

A

A category of wireless communication that covers low-power long-range connection.

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29
Q

LoRaWAN

A

LPWAN Technology

Low Power Long Range Wide Area Network

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30
Q

LoRaWAN Cost

A

Expensive

Proprietary Physical Layer
Pricey Gateways

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31
Q

LoRaWAN Transmission Speeds

A

50 kbit/s
Slow

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32
Q

LoRaWAN Packet Size

A

256 bytes

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33
Q

LoRaWAN Range

A

10km

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34
Q

LoRaWAN Power

A

Low

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35
Q

LoRaWAN Layer

A

Data Link & Physical

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36
Q

LoRaWAN Topology

A

Star-of-Stars

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37
Q

LoRaWAN Advantages

A

Uses Chirp Modulation
- Doppler Resistant: Ideal for moving objects
- Interference Resistant
- Multipath Resistant
- Highly Scalable

Uses IP for communication between Gateways and Cloud Services

Uses sub-GHz frequencies that penetrate obstacles and don’t collide with other communication protocols

Up to 10km range in rural areas

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38
Q

LoRaWAN Disadvantages

A

Proprietary PHY Layer

Relatively Low Data Rate

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39
Q

Sigfox

A

LPWAN Technology

Uses Ultra Narrow Band modulation for very slow data transmission

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40
Q

NB-IoT

A

LPWAN Technology

Uses a low-cost sim-card within a narrowband of 4G LTE and 2G GSM for 4x faster speeds than LoRaWAN. Used in Asset Tracking

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41
Q

Nano Satellites

A

LPWAN Technology

Low Earth Orbit satellites that forward data from devices onto ground stations. Requires subscription

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42
Q

LTE-M

A

LPWAN Technology

Uses 4G LTE for 1Mbit/s speeds at relatively high-power consumption

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43
Q

Bluetooth

A

Short range, personal area network wireless communication technology

2.4GHz band is divided into 79 Bluetooth channels, communication is divided into 1600 time slots per second

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44
Q

Bluetooth Layer

A

Data Link & Physical

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45
Q

Bluetooth Range

A

1m - 100m

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46
Q

Bluetooth Transmission Speeds

A

1 Mbit/s

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47
Q

Bluetooth Power

A

Low if BLE

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48
Q

Bluetooth Topology

A

Star

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49
Q

Bluetooth Cost

A

Inexpensive

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50
Q

Bluetooth Piconet

A

One controller forms up to seven active connections with responders creating a Piconet

Up to 255 responders can be parked, maintain a connection but not communicating

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51
Q

Bluetooth (Adaptive) Frequency Hopping

A

Reduces interference by having transmission hop between channels.

Adaptive Frequency Hopping avoids channels in use such as those used by Wi-Fi

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52
Q

Bluetooth GATT Profile

A

GATT Profiles standardise exchange of data for specific device types e.g. Heart Rate Sensor

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53
Q

Bluetooth Advantages

A

Frequency hopping improves security as all channels must be sniffed

Interleaving allows communication with multiple responders

TDMA allows contention-free networking

Ubiquitous integration among devices

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54
Q

Bluetooth Disadvantages

A

Operates in unlicensed 2.4GHz ISM band, interference prone

Relatively low data rate

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55
Q

802.15.4

A

A standard covering specification of the Physical and Data Link layers for low-rate wireless PANs

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56
Q

802.15.4 Layer

A

Data Link & Physical

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57
Q

802.15.4 Range

A

<100m

58
Q

802.15.4 Transmission Speeds

A

250 kbit/s

59
Q

802.15.4 Power

A

Very Low

60
Q

802.15.4 Topology

A

Star & Peer-to-Peer

61
Q

802.15.4 Cost

A

Inexpensive

62
Q

802.15.4 Packet Size

A

127 bytes

63
Q

802.15.4 PAN Coordinator

A

Acts as a central network controller

64
Q

802.15.4 Coordinator

A

Provide synchronisation services to devices

65
Q

802.15.4 FFD

A

Full Function Device

Capable of acting as a PAN Coordinator and can associate with multiple devices simultaneously

66
Q

802.15.4 RFD

A

Reduced Function Device

Capable of associating with only one FFD at a time
Suitable for simple sensors or actuators

67
Q

802.15.4 Routing

A

Routing between devices not in range of each other is not handled by 802.15.4 and instead is handled by higher-layer protocols e.g. RPL

68
Q

802.15.4 Addressing

A

Uses 64-bit MAC addresses and (sometimes) a 16-bit address valid only within the PAN

69
Q

802.15.4 Advantages

A

Low cost, Low power: Ideal for IoT and Sensor Networks

Peer-to-Peer topology acts as a basis of mesh networking allowing for self-healing, self-organising networks

70
Q

802.15.4 Disadvantages

A

Relatively low data rate

Operates in 2.4GHz, prone to interference

71
Q

802.15.4 Duty Cycling

A

Alternates radio between active/idle to save power

72
Q

802.15.4 ContikiMAC

A

An asynchronous duty cycling protocol has retransmissions until the receiver periodically wakes up and responds with an acknowledgement

73
Q

802.15.4 TSCH

A

Time-slotted Channel Hopping

A synchronous duty cycling protocol (defined in the 802.15.4 standard ) that divides time into slots assigned for communication between two specific devices.
Devices synchronise their schedule and use different channels to avoid interference

74
Q

Zigbee

A

A specification of the application and network layer to facilitate mesh and multi-hop networking
Builds on 802.15.4

75
Q

Zigbee Layer

A

Application & Network

76
Q

Zigbee Power

A

Very Low

77
Q

Zigbee Advantages

A

Zigbee-certified devices have a battery life of at least 2 years

Enables mesh networking

78
Q

Zigbee Disadvantages

A

Non-IP

Certification required to add Zigbee logo to device

79
Q

6LoWPAN

A

A specification of the network layer to allow IPv6 over 802.15.4 addresses

Builds on 802.15.4

80
Q

6LoWPAN Layer

A

Network

81
Q

6LoWPAN Advantages

A

IPv6 Compatible allowing for Interoperability

Small headers

82
Q

Thread

A

A standard that provides encrypted, self-healing, resilient mesh networking

Uses 6LoWPAN

83
Q

RPL

A

IPv6 Routing Protocol for Low-Power and Lossy Networks

An IPv6 Routing Protocol suitable for routing over mesh networks, allowing for multi-hop networking

Builds on 802.15.4

84
Q

RPL Layer

A

Network

85
Q

RPL Topology

A

Uses network traffic to build a picture of network (traffic decreases as network stabalises)

Creates a tree-like DODAG topology and assigns a distance-dependent rank to nodes further from the root to prevent routing to closer nodes via farther nodes

86
Q

MQTT

A

A lightweight publish-subscribe messaging protocol

87
Q

MQTT Layer

A

Application

88
Q

MQTT Broker

A

Brokers forward messages from publishers onto appropriate subscribers

Clients connect to the broker using Wi-Fi typically and transfer JSON

89
Q

MQTT Topics

A

Topics are hierarchical
- # acts as a multi-level wildcard
- + acts as a single level wildcard

90
Q

CoAP

A

A lightweight RESTful messaging protocol designed for resource-constrained devices

Follows REST principles, providing interoperability with HTTP (and the Web)
Border gateways/proxies translate between HTTP and CoAP

91
Q

CoAP Layer

A

Application

92
Q

CoAP Request Types Support

A
  • Confirmable (requiring acknowledgement) requests
  • Non-confirmable requests
  • Timeouts
  • Delayed payload responses with tokens
  • Resource observation
  • Block transfers for large payloads
93
Q

CoAP Resource Discovery

A

Request to GET .well-known/core returns descriptions of resources available on nodes allowing for automatic configuration

94
Q

CoAP Advantages

A

Small packet size; header is fixed-size at 4 bytes

Highly suited for use with 802.15.4, a basic packet will fit into a single radio frame

Uses UDP, ideal for prolonging battery life

CoAP proxies cache data allowing nodes to sleep

Supports multicast allowing interactions with multiple nodes at once

95
Q

Matter

A

A unifying application layer that leverages existing communication standards. It specifies
- Device Onboarding
- Device Messaging
- Security

Sits on-top of Thread, Ethernet, Wi-Fi, Bluetooth and unifies interactions

96
Q

Matter Layer

A

Application

97
Q

Matter Advantages

A

Non-matter devices can be bridged into a Matter network

Big-players in home automation are onboard

98
Q

Improving Wi-Fi

A

Modulation Techniques
Spatial Performance Improvements
Multiple Access
Wi-Fi 6

99
Q

Wi-Fi Modulation Techniques

A

DSSS
FDM
OFDM
OFDMA

100
Q

Wi-Fi Spatial Performance Improvements

A

Beamforming
MIMO
MU-MIMO

101
Q

Wi-Fi Multiple Access

A

CSMA/CD (Ethernet)
CSMA/CA (Wi-Fi)

102
Q

IPv4 Exhaustion Mitigitation

A
  • Address Conservation: RIRs avoid giving out large blocks of address space
  • Network Address Translation (NAT): Multiple private IPs, one public IP
  • Release of Reserved Address Space: Challenging as client configurations need updating
  • Address Recovery: Challenging as reputation of IP must be recovered
  • CGNAT: ISP shares single IP address among multiple homes
103
Q

CGNAT Issues

A

Breaks end-to-end connectivity
Public IP abuse causes multiple homes to be punished
Security and privacy implications
Scalability issues
Does not solve IPv4 exhaustion

104
Q

Reasons for lack of IPv6 Adoption

A

Hardware
Infrastructure
Training

Lack of Urgency
Implementation Challenges
Money

HInT LimM

105
Q

IPv6 Benefits

A

Resolves IPv4 Exhaustion
Direct end-to-end global addressability
Simplified networks with reduced latency

106
Q

IPv6 DNS Adoption

A

IPv4 DNS servers can serve AAAA (IPv6) records and vice-versa

107
Q

Dual Stack Deployment

A

Supporting of both IPv4 and IPv6 protocols with devices having addresses in both forms

108
Q

Dual Stack Deployment Issues

A

Essentially two networks running in parallel:
- Each protocol needs its own firewall
- More issues to troubleshoot
- Double the IP config
- More hardware usage e.g. routing table

109
Q

IPv6 Deployment Strategy

A
  1. Plan Ahead
  2. Comprehensive Planning
  3. Initial IPv6 Deployment During a Network Upgrade (Reduces cost)
  4. Aim to keep parity of service no matter the strategy (No not damage IPv4 performance)
110
Q

Imperial College IPv6 Deployment

A

Deployed a dual-stack system
Used SLAAC as DHCPv6 was not well supported and still is not supported on Android
Has both IPv6 and IPv4 used on the same network
Switched early for to lower cost

Motivation was from CERN requiring IPv6 and they were running out of IPv4

111
Q

Microsoft IPv6 Deployment Case Study

A

RFC1918 (Private Network) Address space is running out due to overlapping from acquired companies and their networks
Dual-stack is operationally complex and hence Microsoft’s desire to switch to IPv6 solely

112
Q

IPv6 Transition Mechanisms

A

Tunnelling
NAT64
VPN

113
Q

IPv6 Tunnelling

A

Encapsulates IPv6 packets in IPv4 packets between two destinations
- Reduces MTU
- Increases Latency
- Causes issues with GeoIP-restricted services

114
Q

6in4 Tunnelling

A

Adds IPv4 header in front of IPv6 packet
- Protocol 41 is not supported by many consumer routers and so they cannot provide options to support it

115
Q

NAT64

A

Embeds IPv4 DNS web addresses within an IPv6 address with a specific prefix
- DNS64 Servers synthesise AAAA records for a web domain that only has A records
- NAT64 Gateway translates packets with the specified prefix to IPv4

116
Q

NAT64 Example

A
  1. User requests IP of URL from DNS64 server
  2. The DNS64 server does not know the IP and contacts a DNS server which returns an A record IPv4 address
  3. The DNS64 server prefixes the IPv4 address to create a AAAA record
  4. The user contacts the IP address via a NAT64 gateway which strips the prefix and contacts the IPv4 web server
117
Q

464XLAT

A

Allows IPv4 Connectivity over an IPv6 Network with two translators
- Stateless Customer Translator (CLAT): Converts IPv4 to IPv6
- Stateful Provider Translator (PLAT): Converts back to IPv4. Must track connections, ports, addresses etc.

118
Q

Google IPv6 Transition Case Study

A

Uses 464XLAT with DHCPv4 Option 108

119
Q

DHCPv4 Option 108

A

Devices are either
- In need of IPv4
- Capable of operating IPv6 only

Devices capable of IPv6 only send DHCP requests with Option 108 which indicates IPv4 is not necessary if IPv6 is available
- DHCPv4 servers will not provide IPv4 address if Option 108 is specified and supported. Forcing a device to use IPv6

120
Q

Steps of the Mandiant Cyber Attack Life Cycle

A
  1. Initial Recon
  2. Initial Compromise
  3. Establish Foothold
  4. Escalate Privileges
  5. Internal Recon
  6. Move Laterally
  7. Maintain Presence (Loop back to 4.)
  8. Complete Mission
121
Q

Initial Recon

A

Scope out a target through methods such as

  • Port & Network Scanning: Identify open ports
  • Banner Grabbing: Extract information on system software versions and configurations
  • Signature Recognition: Different versions of software respond in different ways
  • DNS Brute Forcing: Look for common subdomains i.e. vpn.xyz or login.xyz and reverse DNS
  • Dumpster Diving: Physical rummaging through discarded documents or hardware (network switches, hard drive etc. need to be wiped)
  • Social Engineering: Psychological manipulation to deceive individuals
  • Man-in-the-Middle: Intercept communication
  • Google & Shodan: Identify publicly available information
122
Q

Defending Against Initial Recon

A

Difficult to defend as malicious recon blends in with normal network traffic

Security through obscurity can impede an attacker

123
Q

Initial Compromise

A

Execute malicious code on the target’s system using
- Social Engineering
- Remote Execution: SQL Injection
- Brute Force
- Password Reuse

124
Q

Defending Against Initial Compromise

A

User Education
Appropriate technical methods

125
Q

Establish Foothold

A

Gain some level of control over a target system using
- Rootkits
- Backdoors
- Introduction of further vulnerabilities

126
Q

Defending Against Establish Foothold

A

Block vulnerabilities
Update Systems

127
Q

Escalate Privileges

A

Gain more control by increasing privileges and eventually gaining root access using
- Exploitation of privilege escalation vulnerabilities
- Dumping and cracking hashed passwords/access password managers

128
Q

Defending against Escalate Privileges

A

Implement Least Privilege Principle, Minimum level of access to perform necessary tasks
MFA

129
Q

Internal Recon

A

Gain a more thorough understanding of the target’s network and systems
- Where are key files stored
- What is known about key individuals (for social engineering)
- What internal systems are used?

130
Q

Defending against Internal Recon

A

Network segmentation

131
Q

Move Laterally

A

Gain more access to more systems

132
Q

Defending against Move Laterally

A

Firewalls

133
Q

Maintain Presence

A

Establish persistent access
- Additional rootkits
- Multiple backdoors
- Deploy more malware
- Gain access via existing legitimate remote access services/VPN

134
Q

Defending against Maintain Presence

A

Network monitoring and audits

135
Q

Complete Mission

A
136
Q

Security Policies

A

Identify the rules and procedures for people and systems accessing networks and sets out responsibilities of those managing networks

137
Q

A good security policy should

A
  • Ensure confidentiality, integrity and availability of systems
  • It should be organisation specific, practical, enforceable and regularly updated
  • It should include processes for users to report security issues and detail how issues will be responded to and who is responsible
  • It should define a password policy
  • It should cover incident responses, who’s is responsible
138
Q

A bad security policy will

A
  • Encourage users to be less secure
  • Users who dont understand the goal of the policy are less likely to apply it
  • Users who feel it hinders their work are more likely to bypass it
  • Users who feel security is driven from top-down are less likely to report incidents
139
Q

Employee Training

A

Employees should be educated on
- Why you shouldn’t bypass security policies
- Phishing
- Fake websites
- Malicious Downloads

140
Q

Ongoing Network Maintenance

A

Updated devices often have less vulnerabilities
- OS Patches
- Drivers, Firmware, BIOS updates
- Mobile device firmware
- Routers
- IoT firmware

141
Q

IP Reputation

A

Block or alert on access from IP known for malware/botnets, or dodgy URLs
Geographic IP restricts e.g. restrict incoming Russian traffic

University (12 decks)

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