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Note for Cyber Security - cs by nainish aggarwal

  • Cyber Security - cs
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  • Dr. A PJ Abdul Kalam Tech University Lucknow - AKTU
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Information system development The systems development life cycle (SDLC), also referred to as the application development lifecycle, is a term used insystems engineering, information systems and software engineering to describe a process for planning, creating, testing, and deploying an information system. [1] The systems development life-cycle concept applies to a range of hardware and software configurations, as a system can be composed of hardware only, software only, or a combination of both. Overview A systems development life cycle is composed of a number of clearly defined and distinct work phases which are used by systems engineers and systems developers to plan for, design, build, test, and deliver information systems. Like anything that is manufactured on an assembly line, an SDLC aims to produce high quality systems that meet or exceed customer expectations, based on customer requirements, by delivering systems which move through each clearly defined phase, within scheduled time-frames and cost estimates.Computer systems are complex and often (especially with the recent rise of service-oriented architecture) link multiple traditional systems potentially supplied by different software vendors. To manage this level of complexity, a number of SDLC models or methodologies have been created, such as "waterfall"; "spiral,prototype model incremental". Waterfall model: Waterfall approach was first SDLC Model to be used widely in Software Engineering to ensure success of the project. In "The Waterfall" approach, the whole process of software development is divided into separate phases. In Waterfall model, typically, the outcome of one phase acts as the input for the next phase sequentially. Following is a diagrammatic representation of different phases of waterfall model. KAMNA SINGH CYBER SECURITY NOTES Page 2

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The sequential phases in Waterfall model are: • • • • • • Requirement Gathering and analysis: All possible requirements of the system to be developed are captured in this phase and documented in a requirement specification doc. System Design: The requirement specifications from first phase are studied in this phase and system design is prepared. System Design helps in specifying hardware and system requirements and also helps in defining overall system architecture. Implementation: With inputs from system design, the system is first developed in small programs called units, which are integrated in the next phase. Each unit is developed and tested for its functionality which is referred to as Unit Testing. Integration and Testing: All the units developed in the implementation phase are integrated into a system after testing of each unit. Post integration the entire system is tested for any faults and failures. Deployment of system: Once the functional and non functional testing is done, the product is deployed in the customer environment or released into the market. Maintenance: There are some issues which come up in the client environment. To fix those issues patches are released. Also to enhance the product some better versions are released. Maintenance is done to deliver these changes in the customer environment. All these phases are cascaded to each other in which progress is seen as flowing steadily downwards (like a waterfall) through the phases. The next phase is started only after the defined set of goals are achieved for previous phase and it is signed off, so the name "Waterfall Model". In this model phases do not overlap. Waterfall Model Application Every software developed is different and requires a suitable SDLC approach to be followed based on the internal and external factors. Some situations where the use of Waterfall model is most appropriate are: KAMNA SINGH CYBER SECURITY NOTES Page 3

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• • • • • • Requirements are very well documented, clear and fixed. Product definition is stable. Technology is understood and is not dynamic. There are no ambiguous requirements. Ample resources with required expertise are available to support the product. The project is short. Waterfall Model Pros & Cons Advantage The advantage of waterfall development is that it allows for departmentalization and control. A schedule can be set with deadlines for each stage of development and a product can proceed through the development process model phases one by one. Development moves from concept, through design, implementation, testing, installation, troubleshooting, and ends up at operation and maintenance. Each phase of development proceeds in strict order. Disadvantage The disadvantage of waterfall development is that it does not allow for much reflection or revision. Once an application is in the testing stage, it is very difficult to go back and change something that was not welldocumented or thought upon in the concept stage. The following table lists out the pros and cons of Waterfall model: Pros • • • • • • • • Simple and easy to understand and use Easy to manage due to the rigidity of the model . each phase has specific deliverables and a review process. Phases are processed and completed one at a time. Works well for smaller projects where requirements are very well understood. Clearly defined stages. Well understood milestones. Easy to arrange tasks. Process and results are well documented. Cons • • • • • • • • • • KAMNA SINGH No working software is produced until late during the life cycle. High amounts of risk and uncertainty. Not a good model for complex and objectoriented projects. Poor model for long and ongoing projects. Not suitable for the projects where requirements are at a moderate to high risk of changing. So risk and uncertainty is high with this process model. It is difficult to measure progress within stages. Cannot accommodate changing requirements. No working software is produced until late in the life cycle. Adjusting scope during the life cycle can end a project. Integration is done as a "big-bang. at the very end, which doesn't allow identifying any technological or business bottleneck or CYBER SECURITY NOTES Page 4

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challenges early. [2] prototype model : he basic idea here is that instead of freezing the requirements before a design or coding can proceed, a throwaway prototype is built to understand the requirements. This prototype is developed based on the currently known requirements. By using this prototype, the client can get an “actual feel” of the system, since the interactions with prototype can enable the client to better understand the requirements of the desired system. Prototyping is an attractive idea for complicated and large systems for which there is no manual process or existing system to help determining the requirements. The prototype are usually not complete systems and many of the details are not built in the prototype. The goal is to provide a system with overall functionality. The prototyping model is a systems development method (SDM) in which a prototype (an early approximation of a final system or product) is built, tested, and then reworked as necessary until an acceptable prototype is finally achieved. Advantages of Prototype model: • • • • • • Users are actively involved in the development Since in this methodology a working model of the system is provided, the users get a better understanding of the system being developed. Errors can be detected much earlier. Quicker user feedback is available leading to better solutions. Missing functionality can be identified easily Confusing or difficult functions can be identified Requirements validation, Quick implementation of, incomplete, but functional, application. Disadvantages of Prototype model: • • Leads to implementing and then repairing way of building systems. Practically, this methodology may increase the complexity of the system as scope of the system may expand beyond original plans. KAMNA SINGH CYBER SECURITY NOTES Page 5

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