Welcome to a lecture on the security of operating systems the first module in the series will focus
on operating system security models illustrated by Windows systems.
We will try and answer the following question what level of protection can be offered by an operating
system.
Let's start with basic security.
What sort of protection can be expected from operating systems
an operating system must above all guarantee the availability of provided services.
We as users need to be sure that the tasks we want to execute will be executed.
We also need to be sure that the system performance will be reliable for example that the system will
not fail
and the aspect that is most relevant in this course is that the data is stored and processed by an operating
system will remain secure and confidential and that its integrity won't be compromised.
Modern operating systems or any of the computers we're used are almost always connected to some network.
There are also almost always connected to the global network the Internet
their environment supports a number of applications which exchange data with external services without
her knowledge.
This is a problem because we have no control or little control over the data that can be found in our
computer and is processed by it.
A good example of this are any viruses or any other programs that update regularly
some developers set the default control to such an aggressive level that an anti-virus checks for virus
database updates multiple times per minute if you monitor network traffic you'll see that your scanner
sends out an update query regularly even every 15 or 20 seconds.
To standardize the security that is provided by a computer system a classification for evaluating security
levels has been introduced.
Initially the assessment criteria of operating system security were published in a document called the
Orange Book.
It was part of a rainbow book series on computer systems security.
Several years later the evaluation standard was updated and systematized.
Today the binding standards are the common criteria for information technology.
The CC norm as you can see there are several standard categories.
The table above shows relationships or the corresponding security levels under the Orange Book and the
Common Criteria standards.
Let's start with the most basic systems.
This is the division or the first e-mail level
to be classified at this level an operating system doesn't have to offer any guarantee of protection.
The system doesn't support for example the separation of user sessions.
This means that the physical address to the computer means defacto gaining full control over the system.
This includes the ability to open and modify other users data to give you an example the Windows 9x
serious systems are classified at this level.
The second level provides for discretionary data protection a system is required to authenticate an
authorized users in a secure manner once identification is completed prior to executing each command.
A user will be verified for having appropriate privileges to run it.
Early Linux and Unix systems are classified at this level.
The third level systems enforce access control adding to the features supported in level two systems
systems classified at this level are required to provide for user activity monitoring each allowed or
disallowed operation has to be logged.
An example of a system class at this division is Windows A.E.
the fourth level is restricted to systems that support labelled security protection.
It's an implementation of a model known in cryptography.
The security theory has the bell Lapa doula model will come back to this in the future.
In a nutshell the model assigns sensitivity levels for certain types of data.
A person with a given level of privileges will be able to access only the data that was assigned to
the corresponding or lower sensitivity label.
Newer Windows and Linux systems are classed at this level the fifth level also enforces structured protection
it requires the operating system structure to allow for the monitoring and control of all operations
executed by the system.
This means that the uncontrollable tampering with data of another process is impossible.
All launched operations are atomic operations and the access to the data processed by it must be authorized.
The fifth level doesn't encompass popular operating systems.
They don't even aspire to it.
Some specialized versions of systems implemented on specific machines may be classed at this level.
The six level systems required the provision of process isolation
each security critical operation must be separate and independent in the system.
The highest level the seventh level is assigned to those systems that are able to formally for example
mathematically verify their security the systems have to effectively exclude any possibility of successful
attacks.
The security of these systems can't depend on configuration or user behavior.
It has to offer formal assurance of full protection.
Level 7 encompasses several devices not systems.
They're definitely not commercially available.
The modules that deal with operating systems security will talk above all about systems security boundaries.
The concept of a security boundary is vitally important as safeguarding a system against cyber threats
amounts to risk management we've realized this early on during the first modules of the first part of
our course to manage the risks in a conscious manner.
You have to be aware of the protection that is offered by a computer system.
You also need to take note of the fact that an operating system can only protect data when it's running.
It doesn't protect data against local attacks.
We'll try to give you hints on using popular operating systems in a considerably security conscious
way.
And finally we'll also take a look at the concept of granting rights to users.
What did the programs launched by users this different security model's been supported for many years
and many computer systems also in Windows systems.
The security model we just mentioned a model that is based on code on access rights is on the shelf
but seldom used.
This means that it's the task of the administrator to stop users from launching any potentially harmful
programs.
In the next lecture of this series we'll learn about the implementation of this.
We'll also take a look at the techniques and tools for independent detection and removal of malware.
The malware we refer to are mostly root kits programs that attempt to hide from users and administrators.
At the end will evaluate the security of our systems configuration errors are in practice the largest
source of problems with the protection measures effectiveness users and administrators often don't modify
the default configuration of living it's set to provide the highest security which is not true.
Or sometimes reconfigure their systems in a way that lowers the security even further.
See you in the training.