CSG Meeting 02/27 Understanding how computers communicate data over the wire and what is done to secure that data from malicious actors.

1. Computer Networks
and
Network Security
2019/02/27

2. Announcements
● Firetalks 03/27
● No meeting next week, DHA. 03/06

3. What is a computer network?
● Defined as a digital telecommunication network which
allows nodes to share resources.
● Machines will create connections between each other and
exchange data.
● These links can be physical cables such as copper or fiber
optic or could be wireless such as Wi-Fi.

5. Level 2 - Medium Access Control
● Reliable transmission for data frames between two nodes connected by a
physical layer.
● Responsible for:
○ Frame receiving and transmitting.
○ Addressing of destination stations.
○ Conveying source station addressing information.
○ Control of access to the physical transmission medium.
● The final layer of encapsulation before the data is transmitted over the
physical layer.

6. Media Access Control Addresses
● The Media Access Control (MAC) address of a device is a
unique identifier assigned to a network interface controller.
○ Ex. 40:a3:cc:a8:4e:36
● All MAC address are unique for every network interface
controller.
● Think of it as the machines social security number.

7. Level 3 - Network Layer
● Structuring and managing multi node network.
● Responsible for packet forwarding and routing.
○ Routing - Determining the logical path that data will take to reach its
destination
○ Forwarding - Determine the next device to send the data to on the
defined route.
● Provides the functionality and procedures for transferring packets from one
node to another.
● One such protocol that sits at this layer is known as IP

8. Internet Protocol
● The principal communications protocol for relaying datagrams across network
boundaries.
● Tasked with delivering packets of data from the source host to destinations
based on IP addresses.
● The IP will encapsulate the applications data with data that is necessary for
the packet to be delivered.

9. IP Addressing
● An IP address is a numerical label to each device connected to a computer
network using the IP protocol.
○ Assists with host interface identification and location addressing in the
network..

10. Layer 4 - Transport layer
● Transmission of data segments between points on a network.
● Contain quality of service functions such as flow control, segmentation, and
error control.
○ Acknowledgement of successful transmissions
○ Retransmissions of failed data segments/datagrams.

11. TCP/UDP
● Transmission Control Protocol provides connection-oriented, reliable,
ordered, and error-checked delivery of stream octets between hosts.
○ Ex. Youtube videos/Netflix
● User Datagram Protocol is a connectionless, unreliable, unordered, and no
error checked delivery of datagrams between hosts.
○ Ex. Live streams

12. Wireshark Demo

13. WHAT ABOUT THE SECURITY?!?!?!
Well there is a lot different areas and types of network security out there..
● IPSec
● DNSSEC
● Malware Prevention
● Firewalls
● IDS/IPS
● Network Segmentation
● Web Security
● Wireless Security
● Etc.

14. Malware Prevention
● This involves setting up network infrastructure to identify and detect the
presence of intrusions on the network.
○ I.E. Malicious traffic or malicious behaviour
● Possible signs of malicious behaviour at the network level
○ Machines communicating to outside machine constantly (C&C).
○ Local machines communicating when they are not known to.
○ Out of the ordinary network traffic. (Sketchy sites)

15. Well known virus attacks
● CryptoLocker
● ILOVEYOU
● MyDoom
● Storm Worm
● Zeus Trojan
● Emotet Trojan
● Stuxnet

16. Emotet
https://www.us-cert.gov/ncas/alerts/TA18-201A

17. Resources
● Learning areas
○ HacktheBox.eu
○ https://www.sans.org/network-security/#free
○ Hacking the art of exploitation
● Tools
○ Wireshark
○ Nessus
○ Aircrack-ng
○ Snort