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nurul afzan

on 6 October 2013

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Real-time embedded systems
Multimedia Systems
Handheld Systems
Operating systems !

Operating systems
A collection of software that manages computer hardware resources and provides common services for computer programs.
The operating system is an essential component of the system software in a computer system.
Application programs usually require an operating system to function.
Distributed Systems
A collection of autonomous computers
a) linked by a network
b) using software to produce an integrated computing facility
Role of Operating Systems in Security
Protecting systems from deliberate attacks, either internal or external.
Protecting against system threats in operating system.
Protection against program threats.
Operating system as a security tool via cryptography.
Special-Purpose Systems
Done by:
Distributed Systems
Special-purpose systems
Role of Operating Systems in Security
Real-time embedded systems
Multimedia Systems
Handheld Systems
Role of Operating Systems in Security:
Protecting systems from deliberate attacks, either internal or external.
Protecting against system threats in operating system.
Protection against program threats.
Operating system as a security tool via cryptography.
A system that involves
(production/authoring tools)
(compression and formats)
(file system design)
(networking issues)
search and retrieval
(database management)
(server design, streaming)
of multimedia information.

What is the real-time embedded system?
Embedded System
Processor based
– General processors
– Micro controllers
A subsystem
Not a general programming computer
Not only deliver correct results but when these results are delivered
between real-time embedded systems, multimedia systems & handheld systems.
Example of Application
Resource sharing
Fault Tolerance
Resource Sharing:

hardware - disks and printers
software - files, windows, and data objects
Hardware sharing for:
reduction of cost
Data sharing for:
consistency - compilers and libraries
exchange of information - database
cooperative work - groupware

It can be extended.
Open or closed with respect to hardware or software
- published specifications and interfaces
- standardization of interfaces
UNIX was a relatively open operating system:
C language readily available
System calls documented
New hardware drivers were easy to add
Applications were hardware independent
IPC allowed extension of services and resources


Parallel executions in distributed systems:
Many users using the same resources, application interactions
Many servers responding to client requests

How the system handles growth?
Small system - two computers and a file server on a single network
Large system - current Internet

Software should not change to support growth
Research area (for large, high-performance networks)
Avoid centralization to support scalability
Choose your naming or numbering scheme carefully
Handle timing problems with caching and data replication
Fault Tolerance:

Computers fail therefore we need:
hardware redundancy
software recovery
Increase in availability for services
Network is not normally redundant
Program recovery via the process group

transparency of:
Reliability (fault tolerance)
Incremental growth
Sharing of data/resources

very often a collection of processors can provide higher performance (and better price/performance ratio) than a centralized computer.

many applications involve, by their nature, spatially separated machines (banking,commercial, automotive system).
Reliability (fault tolerance):

if some of the machines crash, the system can survive.
Incremental growth:

as requirements on processing power grow, new machines can be added incrementally.
Sharing of data/resources:

shared data is essential to
many applications (banking, computer supported cooperative work, reservation systems); other resources can be also shared
e.g: expensive printers

facilitates human-to-human communication.

Access transparency:

local and remote resources are accessed using identical operations.
Location transparency:

users cannot tell where hardware and software resources (CPUs, files, data bases) are located; the name of the resource shouldn’t encode the location of the resource.
Concurrency transparency:

the users will not notice the existence of other users in the system (even if they access the same resources).
Replication transparency:

the system is free to make additional copies of files and other resources (for purpose of performance and/or reliability), without the users noticing.
Example: several copies of a file; at a certain request that copy is accessed which is the closest to the client.
Failure transparency:

applications should be able to complete their task despite failures occurring in certain components of the system.
Migration (mobility) transparency:

resources should be free to move from one location to another
Performance transparency:

load variation should not lead to performance degradation. This could be achieved by automatic reconfiguration as response to changes of the load; it is difficult to achieve.
a lightweight, portable electronic device with a built-in screen, game controls, speakers and replaceable and/or rechargeable batteries or battery pack.
all 3 systems can work together in a same device, which is a smartphone.
all 3 systems normally work in symbiotic manner where they complete ecah other.
E.g: Wechat apps consists of combination of realtime, multimedia and handheld systems.
Multimedia systems not necessarily need real-time systems or handheld systems.
It can stand on its own.
Real-time systems can be an online application form and not consist of both multimedia and handheld systems.
Handheld systems act more as a platform for mobile apps. Whereas the apps installed on handheld systems can be either real-time systems or multimedia systems or combination of both.
Handheld itself consist of both real-time and batch system. (E.g: Network scan is done real-time while system scan for errors happen in batch system.)
Handheld system also can be installed for example azan prayer and qiblat direction (example of real-time multimedia system).

Real-time multimedia systems not necessarily need handheld systems to operate. they can also run on desktop OS such as Windows and Linux.
Differences between real-time system and multimedia system is multimedia system not necessarily real-time. it can be batch system.
Handheld system is a mobile operating system. (E.g: symbian for nokia & android for samsung or other majorities smartphones)
Protecting systems from deliberate attacks, either internal or external from individuals intentionally attempting to steal information, damage information, or otherwise deliberately wreak havoc in some manner.
Protecting against system threats in operating system:
Trojan Horse
Trap Door
Logic Bomb
Protection against program threats:
Port scanning
Denial of Service (DOS)
Operating system as a security tool via cryptography:
Trojan Horse
A Trojan Horse is a program that secretly performs some maliciousness in addition to its visible actions.
Some Trojan horses are deliberately written as such, and others are the result of legitimate programs that have become infected with viruses.

Spyware is a version of a Trojan Horse that is often included in "free" software downloaded off the Internet. Spyware programs generate pop-up browser windows, and may also accumulate information about the user and deliver it to some central site. ( This is an example of covert channels, in which surreptitious communications occur. )
Another common task of spyware is to send out spam e-mail messages, which then purportedly come from the infected user.

Trap Door
A Trap Door is when a designer or a programmer ( or hacker ) deliberately inserts a security hole that they can use later to access the system.

Logic Bomb
A Logic Bomb is code that is not designed to cause havoc all the time, but only when a certain set of circumstances occurs, such as when a particular date or time is reached or some other noticeable event.
A worm is a process that uses the fork / spawns process to make copies of itself in order to wreak havoc on a system.
Worms consume system resources, often blocking out other, legitimate processes.
Worms that propagate over networks can be especially problematic, as they can tie up vast amounts of network resources and bring down large-scale systems.

Port Scanning:
Port Scanning is technically not an attack, but rather a search for vulnerabilities to attack.
The basic idea is to systematically attempt to connect to every known ( or common or possible ) network port on some remote machine, and to attempt to make contact.
Once it is determined that a particular computer is listening to a particular port, then the next step is to determine what daemon is listening, and whether or not it is a version containing a known security flaw that can be exploited.

Denial of Service (DOS):
Denial of Service ( DOS ) attacks do not attempt to actually access or damage systems, but merely to clog them up so badly that they cannot be used for any useful work.
Tight loops that repeatedly request system services are an obvious form of this attack.
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