Note for Cyber Security - CS by Anil Kumar
- Cyber Security - cs
- Note
- Anand engineering college - AEC
- Computer Science Engineering
- B.Tech
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UNIT -1 Information systems: Information systems are the software and hardware systems that support data-intensive applications. Such a system may be as simple as a 3x5 card catalog system on a desk, or a desktop calendar. Or, it may be as complicated as a multi-node computer database system used to manage vast quantities of related information. The six components that must come together in order to produce an information system are: 1. Hardware: The term hardware refers to machinery. This category includes the computer itself, which is often referred to as the central processing unit (CPU), and all of its support equipment’s. Among the support equipment’s are input and output devices, storage devices and communications devices. 2. Software: The term software refers to computer programs and the manuals (if any) that support them. Computer programs are machine-readable instructions that direct the circuitry within the hardware parts of the system to function in ways that produce useful information from data. Programs are generally stored on some input / output medium, often a disk or tape. 3. Data: Data are facts that are used by programs to produce useful information. Like programs, data are generally stored in machine-readable form on disk or tape until the computer needs them. 4. Procedures: Procedures are the policies that govern the operation of a computer system. "Procedures are to people what software is to hardware" is a common analogy that is used to illustrate the role of procedures in a system. 5. People: Every system needs people if it is to be useful. Often the most over-looked element of the system are the people, probably the component that most influence the success or failure of information systems. This includes "not only the users, but those who operate and service the computers, those who maintain the data, and those who support the network of computers." 6. Feedback: it is another component of the IS, that defines that an IS may be provided with a feedback (Although this component isn't necessary to function). Pyramid Diagram of Organizational levels and information requirements: Understanding the various levels of an organization is essential to understand the information required by the users who operate at their respective levels.
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Operational management level: The operational level is concerned with performing day to day business transactions of the organization. Users at this level use make structured decisions. This means that they have defined rules that guides them while making decisions. For example, if a store sells items on credit and they have a credit policy that has some set limit on the borrowing. All the sales person needs to decide whether to give credit to a customer or not is based on the current credit information from the system. Tactical Management Level: This organization level is dominated by middle-level managers, heads of departments, supervisors, etc. The users at this level usually oversee the activities of the users at the operational management level. Tactical users make semi-structured decisions. The decisions are partly based on set guidelines and judgmental calls. Strategic Management Level: This is the most senior level in an organization. The users at this level make unstructured decisions. Senior level managers are concerned with the long-term planning of the organization. They use information from tactical managers and external data to guide them when making unstructured decisions. Types of Information Systems: 1. Transaction Processing Systems A transaction processing system provides a way to collect, process, store, display modify or cancel transactions. Most of these systems allow multiple transactions to take place simultaneously. The data that this system collects is usually stored in databases which can be used to produce reports such as billing, wages, inventory summaries, manufacturing schedules, or check registers. 2. Management Information Systems A management information system is an information system that uses the data collected by the transaction processing system and uses this data to create reports in a way that managers can use it to make routine business decisions in response to problems. Some of the reports that this information system creates are summary, exception and ad hoc reports. All this is done to increase the efficiency of managerial activity. 3. Decision Support Systems A decision support system helps make decisions by working and analyzing data that can generate statistical projections and data models. This system gives support rather than replacing a managers judgement while improving the quality of a managers decision. A DSS helps solve problems while using external data. 4. Expert Systems and Neutral Networks An expert system, also known as a knowledge-based system, is a computer system that is designed to analyze data and produce recommendations, diagnosis and decisions that are
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controlled. A neutral system uses computers to foster the way a human brain may process information, learn and remember that information. 5. Information Systems in Organizations This information system collects, stores and processes data to give an organization real time useful and accurate information. This information system encompasses data gathering information from the people and machines that collect, process, output and store data. Also in the networks that transmit and receive data and the procedures that govern the way data is handled. Development of Information Systems The first development methodology we are going to review is the systems-development life cycle (SDLC). This methodology was first developed in the 1960s to manage the large software projects associated with corporate systems running on mainframes. It is a very structured and risk-averse methodology designed to manage large projects that included multiple programmers and systems that would have a large impact on the organization. Various definitions of the SDLC methodology exist, but most contain the following phases. 1. Preliminary Analysis. In this phase, a review is done of the request. Is creating a solution possible? What alternatives exist? What is currently being done about it? Is this project a good fit for our organization? A key part of this step is a feasibility analysis, which includes an analysis of the technical feasibility (is it possible to create this?), the economic feasibility (can we afford to do this?), and the legal feasibility (are we allowed to do this?). This step is important in determining if the project should even get started.
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2. System Analysis. In this phase, one or more system analysts work with different stakeholder groups to determine the specific requirements for the new system. No programming is done in this step. Instead, procedures are documented, key players are interviewed, and data requirements are developed in order to get an overall picture of exactly what the system is supposed to do. The result of this phase is a systemrequirements document. 3. System Design. In this phase, a designer takes the system-requirements document created in the previous phase and develops the specific technical details required for the system. It is in this phase that the business requirements are translated into specific technical requirements. The design for the user interface, database, data inputs and outputs, and reporting are developed here. The result of this phase is a system-design document. This document will have everything a programmer will need to actually create the system. 4. Programming. The code finally gets written in the programming phase. Using the systemdesign document as a guide, a programmer (or team of programmers) develop the program. The result of this phase is an initial working program that meets the requirements laid out in the system-analysis phase and the design developed in the system-design phase. 5. Testing. In the testing phase, the software program developed in the previous phase is put through a series of structured tests. The first is a unit test, which tests individual parts of the code for errors or bugs. Next is a system test, where the different components of the system are tested to ensure that they work together properly. Finally, the user-acceptance test allows those that will be using the software to test the system to ensure that it meets their standards. Any bugs, errors, or problems found during testing are addressed and then tested again. 6. Implementation. Once the new system is developed and tested, it has to be implemented in the organization. This phase includes training the users, providing documentation, and conversion from any previous system to the new system. Implementation can take many forms, depending on the type of system, the number and type of users, and how urgent it is that the system become operational. These different forms of implementation are covered later in the chapter. 7. Maintenance. This final phase takes place once the implementation phase is complete. In this phase, the system has a structured support process in place: reported bugs are fixed and requests for new features are evaluated and implemented; system updates and backups are performed on a regular basis. The SDLC methodology is sometimes referred to as the waterfall methodology to represent how each step is a separate part of the process; only when one step is completed can another step begin. After each step, an organization must decide whether to move to the next step or not. Rapid Application Development: Rapid application development (RAD) is a software-development (or systems-development) methodology that focuses on quickly building a working model of the software, getting feedback from users, and then using that feedback to update the working model. After several iterations of development, a final version is developed and implemented.
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