Let's start with the basics.
Historically speaking the first security boundary is the physical computer.
A boundary in this case must separate all local computer processes from the outside world.
Once a computer is connected to a LAN and the Internet everything that is external to the machine is
treated as an trusted you'd probably experience this multiple times launching a program from one that
word share if a file is contained in a directory outside of your computer trying to run it will be prompted
with at least one pop up warning stating that the file comes from an untrusted site and can be potentially
harmful to your computer.
Copying the file or downloading it from the internet using Windows Explorer or Internet Explorer 1 to
automatically make it trusted well with explorers mark such files as files that have crossed a security
boundary even if they're currently stored on a C or D drive.
All attempts to run them will display the same warning messages unless you check the files as trusted.
We'll talk about that later
protecting this data entails the control of all data transmissions.
This can be implemented through the use of system firewalls firewalls have been controlling both incoming
and outgoing traffic for some time already.
The goal of establishing this boundary is not however securing a system against local attacks.
The fact that a physical computer is a boundary doesn't mean that it can actually safeguard a system
against people who have access to the computer's keyboard.
Obstacle this boundary is the most vital security wise violating it involves the risk that the system
is infected with an exploit that can be remotely executed or used to take over remote systems.
This is the critical security level
if a breach of this boundary is detected.
A software developer has to release a critical security patch.
The second security boundary is the operating system a single computer can feature more than one system
this technology is known as virtualization.
It's hardly anything new being first developed as an IBM solution in the 60s.
Soon after the first system was virtualise IBM scientific journal described the first exploit that crossed
the boundaries set by an operating system by exploiting a bug in the input output control system.
The exploit enabled the uncontrolled spending of data between virtualise to operating systems
virtualization is managed by a program or a service called a hypervisor.
There's a particular assumption that arose around the model that makes each operating system a separate
system with separate security regardless of whether it's running on a physical computer or in an environment
virtualise by a hypervisor
people believe that it's enough to secure the host system updated.
Run an antivirus.
Pay attention to the files launched in the host you think that these actions will also protect everything
that has been virtualise in the host.
This is a falsehood over Duell systems require the same level of protection and security as a system
that is running on a physical computer.
Violating the security boundaries set by a system entails an immediate release of an important security
update from Microsoft.
This is a significant boundary that requires protection
we'll look at the third boundary a bit more closely this boundary is defined by a user session
it relates to keeping the programs launched by a user on a system from accessing the programs launched
by another user.
This is critical for example in a terminal environment if a user session did not define a security boundary.
Windows wouldn't be able to operate as a terminal server.
This means that if a company has a president and an I.T. staff member would simultaneously connect to
a server they would both have control over each other's processes and be able to read the data modified
by the other user.
This shouldn't happen.
How was the boundary implemented.
Note that all processes launched by the user are running the user session we'll discover this in a moment.
An operating system is still able to tell when a session process has been launched.
System processes.
For example the services that are automatically run with the start of the system have been separated
to run inside their own sessions before the separation.
They executed in the session of the first user who logged in this constituted a critical breach of the
boundary modern systems have amended this situation.
All user processes are now tagged with a specific level of privileges this permissions attachment means
that the process can only be accessed by the user who launched it access control is can be assigned
not only into files folders and registry keys but also to processes
when those tags processes in such a way that only the user who launched them can access the process.
To enforce data isolation processes are bound to their own name spaces to user name spaces.
We've mentioned that this boundary is of key importance to a terminal server.
There is a problem however if a user session really defined the security boundary this would mean that
an administrator doesn't have full control over his own computer since he can't interfere with the process
launched by other users.
This shouldn't happen.
A user session has been set to define a security boundary Well only for standard users.
Users with raised permissions for example administrators are able to cross the boundary within the rules
provided for the boundary.
This is supported by Microsoft
violating a user's session boundary will also entail a release of an important security update.