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- [Instructor] In a discretionary
access control model

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each resource has a
clearly identified owner.

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For example, a user creating a file

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becomes the owner of that file.

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The owner of a resource can
decide at his discretion

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to allow other users

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or subjects access to that resource.

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The owner discretion is
the main characteristic

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of the discretionary access control.

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Now, the owner in fact,

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when assigning a permission,

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should comply with
organization security policy.

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However, the security policy compliance

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is not enforced by the operating system

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or any other entity.

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It's actually enforced by the user itself.

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So when the owner allows
access to a different user,

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will also set the permissions

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for example, you know,

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to rewrite or execute

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for the other specific
resource to the user.

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And now, in a discretionary access model

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users can be organized in groups as well.

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The owner can grant access to a resource,

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to the entire group,

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instead of the actual individual user.

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Also, a permission
attributes will be assigned

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to a resource for that specific group.

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Now, a simple way to implement

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discretionary access control

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is an access control list,

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which is actually
associated to each object.

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Now, most of modern
operating systems today,

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both open source and
commercial operating systems,

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implement a form of discretionary
access control model.

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In this example,

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I'm showing four files
in a Mac OS X system,

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but this will be the same
in a Linux system as well.

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So as you can see, I'm
the owner of all files.

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And I also belong to the staff group,

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and also each of the files
have their own permissions.

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Now, if you're not familiar
with Linux permissions,

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I include a link to a
website that explains

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them in detail here.

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One of the prerequisites of this exam,

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of the executive fundamentals exam,

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is that you are familiar with
the Linux operating system

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and also, you know,

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the file system, and the
permissions of, you know,

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of the file system.

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So, I definitely urge you and
suggest that you actually read

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this article or this website

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if you're not familiar
with Linux permissions.

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Now, going back to
discretionary access control.

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One of the drawbacks of using

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a discretionary access control model,

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is that the security policy
is left to the discretion

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of the data owner.

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And then the data security administration

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has actually limited
access control over it.

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Additionally, with the number of subjects,

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so that means users,
processes, programs, et cetera,

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accessing a large number of objects,

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maintaining the permission by
respecting the need to know,

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and the least privilege

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becomes a complex administration task.

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So, there's a concept of privilege creep,

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and a privilege creep,

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or otherwise known as authorization creep,

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describes an issue that actually
happens fairly frequently

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in large organizations.

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And this issue is that privileges

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that are being assigned to users

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are never revoked when the user does

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not need them anymore,

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or if they actually even,

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the user actually leaves the organization.

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And this definitely goes against
the need to know principle,

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and as well as the least
privilege principle.

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There are a few key concepts related

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to the discretionary access control model.

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The first one is

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that the discretionary access controls

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are controls where
authorization is decided

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by the owner of the object,

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and also in a discretionary
access control system

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access permissions are
associated to the object itself.

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And lastly, access control
is usually enforced

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with access control lists.