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Operating-System concept 7th edition phần 8

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Nếu một lỗi trang xảy ra, nó sẽ xảy ra ở bước này, trước khi bất cứ điều gì được sửa đổi. Di chuyển sau đó có thể xảy ra; WRE biết vi tính và cố gắng để truy cập vào cả hai đầu của cả hai khối. | Exercises 605 15.3 The list of all passwords is kept within the operating system. âThus if a user manages to read this list password protection is no longer provided. Suggest a scheme that will avoid this problem. Hint Use different internal and external representations. 15.4 What is the purpose of using a salt along with the user-provided password Where should the salt be stored and how should it be used 15.5 An experimental addition to UNIX allows a user to connect a watchdog program to a file. The watchdog is invoked whenever a program requests access to the file. The watchdog then either grants or denies access to the file. Discuss two pros and two cons of using watchdogs for security. 15.6 The UNIX program COPS scans a given system for possible security holes and alerts the user to possible problems. What are two potential hazards of using such a system for security How can these problems be limited or eliminated 15.7 Discuss a means by which managers of systems connected to the Internet could have designed their systems to limit or eliminate the damage done by a worm. What are the drawbacks of making the change that you suggest 15.8 Argue for or against the judicial sentence handed down against Robert Morris Jr. for his creation and execution of the Internet worm discussed in Section 15.3.1. 15.9 Make a list of six security concerns for a bank s computer system. For each item on your list state whether this concern relates to physical human or operating-system security. 15.10 What are two advantages of encrypting data stored in the computer system 15.11 What commonly used computer programs are prone to man-in-the- middle attacks Discuss solutions for preventing this form of attack. 15.12 Compare symmetric and asymmetric encryption schemes and discuss under what circumstances a distributed system would use one or the other. 15.13 Why doesn t D ke NNEtkj. N m provide authentication of the sender To what uses can such an encryption be put 15.14 Discuss how the .