CISSP Module 04 – Communications and Network Security

cloud computing team

We are now continuing with our CISSP online training. In Module 03, we learned about trusted computing, computer architecture or CPU, memory, security models and access, common architecture and we went through all the areas of cryptography-starting from its history, through symmetrical and asymmetrical cryptography (its difference and connections), through hybrid cryptography to cryptographic attacks. Also, we talked about IPSec. In the following CISSP training online, we will discuss the great OSI reference model and talk about the communications and network security. Get ready to continue your CISSP course syllabus 2017! Welcome to the world of network protocols, connectivity devices, threats to network security and much more awaits you in this Module!

OSI and the Seven Layers

If we’re going to talk about various models of networking, and we are going to do it, the best is to start with the OSI Reference Model. OSI stands for Open System Interconnect and has the seven layers. The each layer describes different kinds of its functionality, which are all connected, describing the process called encapsulation (packaging). The goal is the interoperability of diverse communication systems, who have high protocols. As we said it has seven layers, and each layer serves the layer below it. Let us show it on an example-a layer provides error-free communications across a network, providing the path needed by the layers above it. It’s all about transmission and receiving. You need to know them all by name and by number. Those are  application, presentation, session, transport, network, data link, and physical layers.

  • The physical layer is the lowest layer. Concerned with the transmission and reception of the unstructured raw bit stream (over a physical medium). It carries the signal to all the higher layers, describing the electrical or optional, mechanical and functional interfaces.
  • The data link layer is providing error-free transfer of data frames. It does it through one node to another over the physical layer.
  • The network layers have a mission of controlling the operation of the subnet and deciding which physical data should take based on the network on network priority service, conditions or any other factor.
  • The transport layer. It ensures that message is delivered (error free, with no losses or duplications).
  • Session layer allows establishment between processing, which is running on different stations.
  • The presentation layer formats data which are to be presented to the application layer. It’s the translator for the network.

And finally, application layer, serving as the windows for users and application process, providing for accessing the network services.

TCP IP Model

Besides the model we discussed above, there is also another model but divided into four layers. The application layer is the same as for OSI model, host to host or transport layer (of TCP/IP), is the same as the session layer of OSI model. Interwork layer goes with the network, and the network access or network interface goes with the physical OSI model. It is always preferred to use OSI model over the TCP/IP if you can choose.

Common Attacks

Now when we discussed the models, we can talk about threats to network security. You might be heard of some of them, but we will give you a list anyway. There is a Virus, a Worm, Trojan Horse, Logic Bomb and Back Door Programs.

A virus is a malicious code that needs a host in which to live. The worm is similar, but it doesn’t need a host, it’s self-replicating. Logic bomb lays dormant until a logical event occurs. Trojan Horse is a program which is masked and pretending to be some other program. Back door programs bypass normal security controls. These are the most common, but there are many others such as Salami, Data Diddling, Session Hijacking, Sniffing, and Wardialing, Ping of Death and much more.

Firewall, Proxies, and NAT

The main jobs of Firewalls are to allow or block the traffic. It has three layers-the layers 3, 5 and 7. Best and most easily described the layer 3 is the same as the ISO model’s layer protocol. State Full Firewalls are contest depended ones. It has a dynamic filter and similar capabilities.

What is the difference between the Proxy and the NAT? NAT stands for ”Network Adress Translation”. It’s done by routers and firewalls. The computer which shares a network can talk to other computers. However, this local IP addresses must be translated, to a publicly routable address. Proxies are run by a server and can also cache. Proxies are used in the corporate world


WAN stands for Wide Area Networks. It’s a data communications network that covers a broad geographic area, often using transmission facilities provided by common carriers. It functions as the lower three layers of ISO, so the best advice I have for you for better understanding everything in this topic is to-master the ISO model.



There is much more than only Wi-Fi that can be discussed here. It’s important to know that the wireless devices to connect to each other must use the same channel. Besides that, they are configured to use the specific SSID. Wi-Fi routers fall into two categories. It has to with speed of the network they will create when setting up. 802.11g is an older version, IEEE technical terms for wireless networks. But today, there is a newer and of course faster technology-802.11n. Such routers can deliver transfer rates that are up to four or five times faster than the previous one. I won’t finish this before saying this-what about your security? Nowadays, all the routers have built in safe system, but it’s a good thing to remember to enable it when you set up your Wi-Fi network.

Cloud Computing

What is the main job of cloud computing? It’s  providing the shared computer processing the resources and other data to other computers or devices. It allows companies to avoid upfront infrastructure cost. It also enables organizations to focus on their business instead of spending their time on computer infrastructure. Service models are SaaS, PaaS and IaaS.

cloud computing team

Here is your next exam! The Communication & Network Security Skill Certification Test! It is consist of 40 questions and you have one hour to complete it. The skill level is beginner.

Hope we informed you a bit more, and got you interested into moving forward! Keep up the good work!

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