Computer networks and network security

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.

4. 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.

5. 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.

6. 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

7. 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.

8. 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..

9. 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.

10. 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

11. Wireshark Demo

12. 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.

13. 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)

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

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

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