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Protection [Operating System]

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Protection is the mechanisms & policies to keep programs & users from accessing or changing stuff they not do. It is internal to OS.
Protection refers to a mechanism for controlling the access of programs, processes or users to the resources defined by a computer system.
Protection ensures that only processes that have gained proper authorization from OS can operate on the files, memory segments, CPU & other resources of a system.

Goals of Protection
The OS consists of a collection of objects (hardware or software). Each object has a unique name & can be accessed through a well defined set of operations. The goal is to ensure that each object is accessed correctly & only by those processes that are allowed to do so.
The guiding principles of Protection are as follow:
1. Principle of least privilege Programs, users & systems should be given just enough privileges to perform their task so that they can’t alter or harm. 2. Separate “Policy” from “Mechanism” Mechanism: The stuff built into the OS to make Protection work. Policy: The data that says who can do what to whom.  
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