2.4 - Network Services

Question 1

DNS server

Answer 1

• Domain Name System
  – Convert names to IP addresses
  – And vice versa
• Distributed naming system
  – The load is balanced across many different servers
• Usually managed by the ISP or IT department
  – A critical resource

Question 2

DHCP server

Answer 2

• Dynamic Host Configuration Protocol
  – Automatic IP address configuration
• Very common service
  – Available on most home routers
• Enterprise DHCP will be redundant
  – Usually running on central servers

Question 3

File server

Answer 3

• Centralized storage of documents,spreadsheets,
  videos, pictures, and any other files
  – A fileshare
• Standard system of file management
  – SMB (Server Message Block),
  Apple Filing Protocol (AFP), etc.
• The front-end hides the protocol
  – Copy, delete, rename, etc.

Question 4

Print server

Answer 4

• Connect a printer to the network
  – Provide printing services for all network devices
• May be software in a computer
  – Computer is connected to the printer
• May be built-in to the printer
  – Network adapter and software
• Uses standard printing protocols
  – SMB (Server Message Block), IPP (Internet
  Printing Protocol), LPD (Line Printer Daemon)

Question 5

Mail server

Answer 5

• Store your incoming mail
  – Send your outgoing mail
• Usually managed by the ISP or the IT department
  – A complex set of requirements
• Usually one of the most important services
  – 24 x 7 support

Question 6

Syslog

Answer 6

• Standard for message logging
  – Diverse systems, consolidated log
• Usually a central logging receiver
  – Integrated into the SIEM
• You’re going to need a lot of disk space
  – No, more. More than that.

Question 7

Web server

Answer 7

• Respond to browser requests
  – Using standard web browsing protocols - HTTP/HTTPS
  – Pages are built with HTML, HTML5
• Web pages are stored on the server
  – Downloaded to the browser
  – Static pages or built dynamically in real-time

Question 8

Authentication server

Answer 8

• Login authentication to resources
  – Centralized management
• Almost always an enterprise service
  – Not required on a home network
• Usually a set of redundant servers
  – Always available
  – Extremely important service

Question 9

Spam

Answer 9

• Unsolicited messages
  – Email, forums, etc.
• Various content
  – Commercial advertising
  – Non-commercial proselytizing
  – Phishing attempts
• Significant technology issue
  – Security concerns, resource utilization,
  storage costs, managing the spam

Question 10

Spam gateways

Answer 10

• Unsolicited email
  – Stop it at the gateway before it reaches the user
  – On-site or cloud-based

Question 11

All-in-one security appliance

Answer 11

• Next-generation firewall, Unified Threat
  Management (UTM) / Web security gateway
• URL filter / Content inspection
• Malware inspection
• Spam filter
• CSU/DSU
• Router, Switch
• Firewall
• IDS/IPS
• Bandwidth shaper
• VPN endpoint

Question 12

Load balancers

Answer 12

• Distribute the load
  – Multiple servers
  – Invisible to the end-user
• Large-scale implementations
  – Web server farms, database farms
• Fault tolerance
  – Server outages have no effect - Very fast convergence

Question 13

Load balancer features

Answer 13

• Configurable load - Manage across servers
• TCP offload - Protocol overhead
• SSL offload - Encryption/Decryption
• Caching - Fast response
• Prioritization - QoS
• Content switching - Application-centric balancing

Question 14

Proxy server

Answer 14

• An intermediate server
  – Client makes the request to the proxy
  – The proxy performs the actual request
  – The proxy provides results back to the client
• Useful features
  – Access control, caching, URL filtering, content scanning

Question 15

SCADA / ICS

Answer 15

• Supervisory Control and Data Acquisition System
  – Large-scale, multi-site Industrial Control Systems (ICS)
• PC manages equipment
  – Power generation, refining,
  manufacturing equipment
  – Facilities, industrial, energy, logistics
• Distributed control systems
  – Real-time information
  – System control
  – Requires extensive segmentation
  – No access from the outside

Question 16

Legacy and embedded systems

Answer 16

• Legacy systems
  – Another expression for “really old”
  – May also be “really important”
  – Learning old things can be just as important as
  learning the new things
• Embedded systems
  – Purpose-built device
  – Not usual to have direct access to
  the operating system
  – Alarm system, door security, time card system

Question 17

IoT (Internet of Things) devices

Answer 17

• Appliances
  – Refrigerators
• Smart devices
  – Smart speakers respond to voice commands
• Air control
  – Thermostats, temperature control
• Access
  – Smart doorbells
• May require a segmented network
  – Limit any security breaches