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PROCESSING CONTROLS

PROCESSING CONTROLS. Chapter 13. Processor Controls. The most important resource to allocate in a computer system. Four types of controls to reduce expected losses with central processors : Error dtection and correction Multiple execution states Time controls Component replication.

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PROCESSING CONTROLS

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  1. PROCESSING CONTROLS Chapter 13

  2. Processor Controls • The most important resource to allocate in a computer system. • Four types of controls to reduce expected losses with central processors : • Error dtection and correction • Multiple execution states • Time controls • Component replication

  3. Real Memory Controls • To detect and correct errors that occur in memory cells and to protect areas of memory assigned to a program from illegal access by another program

  4. Virtual Memory Controls • The addressing mechanism should check that the memory reference is within the bounds of the block allocated to the process. • An access control mechanism should check to see that the actions a process wants to exercise on a block are within its allowed set of privileges.

  5. Operating System Integrity • A reliable operating system achieves five goals : • It protects itself from user processes • It protects users from one another • It protects users from themselves • It protects itself from itself • It brings operations to an orderly halt in the event of environmental failure

  6. 4 types of threats to operating system integrity : • Privileged personnel abuse their powers. • Would be penetrators deceive privileged personnel into giving them special powers. • Special devices are used to detect electromagnetic radiation, emit electromagnetic radiation, or wiretap communication lines. • Would be penetrators interact with an operating system to determine and exploit a flaw in the system.

  7. Criteria to design, implement and evaluate operating system integrity : • Division D-those that fail to meet the criteria of a higher division • Division C-those that support discretionary access control • Division B-those that support mandatory access control • Division A-those that use formal methods to support specification, design, modelling and analysis of the system

  8. Application Software Controls • 3 level of checks : • Field checks • Record checks • File checks

  9. Audit Trail Controls • Accounting audit trail must allow processing to be traced and replicated. • Operation audit trail is maintained in the processing subsystem.

  10. Existence Controls • An important control in the processing subsystem is a checkpoint/restart facility.

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