 So now we had discussed about encryption and the realm of security in computer networks. Now it's time, let's look at certain topics in computer networks which relate to security. So it's not just security in networks, it's a layered approach. Like security can be at the level of information because information is something that is important and with the networks strive to communicate among each other and so how do we go ahead and ensure security. So to dive deep into security the things we'll be looking at are the CIA tried, then we'll talk about what network security is, then information on data security, then cyber and internet security and then certain securities that relate to the computer, the mobile or IoT security which is more about what are the kind of things you can do for securing your mobiles, your computers or the new generation IoT internet of thing devices. So let's start with what we call the CIA tried. The CIA tried is C for confidentiality, I for integrity and A for availability. So what is confidentiality? Confidentiality is that a certain piece of information is to be available only to the people who are ought to know about it. That means that the information is confidential. Integrity is that the information that is being conveyed is the correct information or in other terms it has not been tampered with. Availability means the information is available to all the relevant people. Now why this is a tried is because when you try to achieve either one of them very extremely you might have to lose on the other two for example. Now if you want to achieve confidentiality and integrity, so you will put more and more measures to secure the information. That means maybe more number of authentications, you will use heavy encryption and all of those. So this will hamper availability. And now if you want the information to be more available to the users, then you will not be able to put on these measures of security, hence you will lose on say confidentiality and integrity though the information will be available. So the key idea is that we have to decide which information lies on which part of the triangle. Now there is something apart from these three which is called non-repudiation. Non-repudiation means that if a person is stating something say he is providing some information, he will not be able to refute this claim later that it was not stated by him or her. So now when we look at the CIA tried, it is a layered approach. Now as we see in the diagram, so we have certain procedures which are at the organization level. Now these procedures ensure that the people who are in the organization comply to all the security. So we have a layered approach towards security here. Now as we see in the diagram, the procedures here ensure that the people who are in the organization are performing all the tasks in compliance with security procedures. And these people then ensure the security of the physical products. So like this way what we see here is there is a layered approach towards it and what are the things that need to be secured? They are the hardware, the software and the communication.