Fundamentals of Computer Systems

The information security has three aims i.e., integrity, confidentiality and availability. They have different meaning with respect to data, information and system. They also address different areas of information security systems. Integrity: Those systems which always provides the correct information about the system. Confidentiality: Those unauthenticated person or software system can’t be able to go through the systems and cannot read/view any confidential information. Availability: The system which provides the access on the information stored to its users when they want so. Generally the terms integrity, confidentiality and availability are loosely construed to be synonymous with security. These however have different connotations with respect to data or information. To understand better the measures and to ensure the protection in those areas, let us define these terms: Security: “Data or information security is the protection of data against accidental or intentional, destructio...

 Information Security means protection of information and information system from unauthorized access, modification and misuse of information or destruction. The basic of information security is to deal with protecting data from people or software having malicious intentions. In this unit we discuss about the factors which are responsible to introduce a threat to an organization system and the defensive mechanisms which can be adopted by the organization against them. As shown in the Figure 1.1, the information security is mainly concerned with the three aspects of data regardless of the form they take data. · Confidentiality · Integrity · Availability We will discuss these terms later in this unit. The terms, information security and computer security frequently are being used interchangeably. Both the fields are related to each other and have the common goals of protecting the information. But there are some differences between the two. The basic difference in both the approaches...

 1.0 INTRODUCTION In today’s, networked society where computer outsells radio and TV, Online shopping is becoming more popular daybyday. The need for providing secure network environments is on top priority for all organizations. Weakness in such a system may lead to all kind of attacks, threat and loss of essential information. Information security deals with how you can secure your personal and confidential information from the rest of the world. In this unit, we will discuss the basic need of information security in an organization. Why do we need to secure our information from the rest of world. Because no one should access it, without your permission or without authentication. We will also discuss about the threats or attacks in breaching of the information security and how easily can a person or software penetrates into your system and accesses your information. After accessing your information, an intruder can manipulate, destroy or misuse your information or data. In this u...

There are wide varieties of computer application in today’s world, without computer networking it is difficult to imagine the world. Few of these applications are described below: Persontoperson communication: Realtime systems, such as videoconferencing and virtual meeting  environments over the network or internet, allow remote users to communicate with no delay, possibly seeing and hearing each others as well. Email : Email is simply the shortened form of electronic mail, a protocol for receiving, sending and storing electronic messages. Email has gained popularity with the spread of the computer network. In many cases, email has become the preferred method of communication. Emails are accessed using through email client software like Outlook, In addition to email client softwares, Webmail has also become very popular. Most email service providers offer this as an additional benefit, where the user can access their mailbox over the Internet. Some email services are specifically d...

 In this section, we will discuss two reference models: 3.6.1 OSI (Open System Interconnection) Model The OSI model is an abstract description for layered communications and computer network protocol design open system means that it can communicate with any other system that follows the specified standards, formats and semantics. PROTOCOLS give the rules that specify how the different parties may communicate. In its most basic form, it divides network architecture into seven layers which from top to bottom are the Application, Presentation, Session, Transport, Network, DataLink, and Physical Layers. It is therefore often referred to as the OSI Seven Layer Model (Figure 7). A layer is a collection of conceptually similar functions that provide services to the layer above it and receives service from the layer below it. On each layer an instance provides services to the instances at the layer above and requests service from the layer below. For example, a layer that provides errorfre...

There are mainly three types of networks: 1) LAN (Local Area Network) 2) MAN (Metropolitan Area Network) 3) WAN (Wide Area Network) 3.5.1 Local Area Network (LAN) LAN (Figure 6) is a group of computers located in the same room, on the same floor or in the same building that are connected to form a single network as to share resources such as disk drives , printers, data, CPU, fax/modem, application. etc. LAN is generally limited to specific geographical area less than 2 K.M., supporting high speed networks. A wide variety of LANs have been built and installed, but a few types have more recently become dominant. The most widely used LAN system is the Ethernet system based on the bus topology. Intermediate nodes (i.e., repeaters, bridges and switches) allow to be connected together to from larger LANs. A LAN may also be connected to another LAN or to WANs and MANs using a “router” device. There are essentially five components of a LAN: 1) Network devices such as Workstations, printers, f...

 In computer networking, topology refers to the layout of connected devices. You can think of a topology as a structure of a network. This shape does not necessarily correspond to the actual physical layout of the devices on the network. Network Topology is the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network interconnection between the nodes. It also determines the strategy for physically expanding the network, in future Topologies can be physical or logical. Physical Topology means the physical design of a network including the devices, location and cable installation. Logical Topology refers to the fact that how data actually transfers in a network as opposed to its design. Following are the considerations for choosing a Topology: · Costing: Some kind of topology may be less expensive compared to others in terms of installation (for example Bus topology). · Length of cable: It is needed to connect machines in a network. · Network scalability:...