Protection and security

Protection and security

Protection in computer system

· In the system with contiguous memory allocation, protection is usually accomplished by the use of limit registers. Each program is assigned a specific limit in term of address space . whenever any reference is made to an instruction of the limit register is checked to ensure that reference is within the bound of program otherwise the access to memory is denied.

· In paging system, protection is achieved by the use of a page table. This page table list all the pages that a program can access.

· In addition the table store access rights such as read, write or execute for each individual page.

· In a system that uses segmentation, protection is accomplished by the use of segment table . each process has its segment table

· In case of files stored on secondary storage devices suchj as disks, access rights are associated with each file system. Any user who tries to access a file may be denied the access depending upon the type of priviledge given to each other

· Security refers to method of protecting information stored in the system, as well as the physical resource of the computer system from unauthorized access , malicious destruction or alteration and accidental introduction of inconsistency

· Authorized users are those, whose identity are known and are allowed to use system resources whereas unauthorized users are those who are not allowed to use system resources.

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