This next video covers the
principle of least privilege. This is the one that
you probably know, although you don't realize it. It's simply, if you've ever
heard the phrase need to know, that's least privilege. You only are told what
you need to know. In the context of computers
it means a subject, which is a process or a user
or an actor of some kind, is only given those rights or privileges that it needs
to complete the task. What's important here is that the functionality is what controls the rights,
not the identity. So, in other words, if I need to read file one and write file two, following this principle,
the process I use to do that would have
no access to file three. In addition, there may be situations in which for a short period of time
I need extra rights. For example, on a Linux system
if I want to open port 25, I can only open
that port as root. But I'm a mail handler, so after that I don't need
root privileges anymore. When my program starts up, it grabs root privileges,
opens port 25, and then drops root privileges
to the mail user. That's another example
of least privilege, just throw it away when
you don't need it. Now, there's
another principle that's closely related to this. It's called POLA, Principle
of Least Authority. Now, POLA and least privilege are often seen as
exactly the same things. However, some people do make a distinction and the distinction
is quite interesting. Principle of least privilege
speaks to permissions. It says, what can I do
to an object, a file? Doesn't say anything about, what can I have you do to it? It's all very direct. What can I do? Authority controls what influence I have over other subjects. So, in other words, can I control how you interact
with that object, for example, or can I control how something
indirectly affects that file? In that case, authority is slightly
different than permission, and so POLA would speak to the authority and least
privilege to the permissions. That distinction is not
widely recognized yet. So, if you hear POLA and
you think least privilege, you're either dead
on or very close, close enough for
our practical purposes unless you're a system developer. All right, now, you'll see this in an exercise
in a little bit. But this puzzle asks whether
or not any Unix-like system like FreeBSD or Linux
or so forth or Windows, does that enforce
least privilege? Think about that for
about half a minute. The answer is basically very direct and we've
talked about this.