*What is computer network? *Types of network *Network topology *Computer components *Network components *Internet security

1. COMPUTER
NETWORK
Networking & Security

2. CONTENTS
 What is a computer network?
 Types of network
 Network topologies
 Computer components
 Network components
 Internet security

3.  A computer network is where two or more networks are
connected or linked. so that they can exchange data.
 Network devices that originate, route and terminate the data
are called network nodes.
 Nodes can include host like servers and personal computers,
as well as networking hardware.
 Two networks are said to networked when a process in one
device can exchange information with a process in another
device.

4.  The connection (network links) between networked computing
device (network nodes) are established using either cable media
or wireless media. The best known computer network is
Internet.
 Computer networks support applications such as world wide
web, shared use of application and storage servers, printers, fax
machine, and use of email and instant text messaging
application.

5. TYPES OF NETWORK
Main Types Of Network:1.
2.
3.
4.
PAN (Personal Area Network)
LAN (Local Area Network)
WAN (Wide Area Network)
MAN (Metropolitan Area Network)

6. PAN - This type of network is used for a portable computer and a
handheld for sharing photos, music, including email and calendar
appointments, short distance connection using USB, Firewire,
Bluetooth or Infrared.
LAN – This type of network is used to connect computers which
belong to the same organization, within a building or small area.
WAN – This type of network is used to connect multiple LAN’s with
each other from far places.
MAN - This type of network is used to connect two or more
computers in nearby cities using fiber optic cable.

8. NETWORK TOPOLOGY
Network topology is the layout or organizational hierarchy of
interconnected nodes of a computer network.
Common layouts: 1. bus network
2. star network
3. ring network
4. tree network
5. mesh network

9. BU S N E T WO R K
 In bus network each node is connected to a single cable.
 A signal from the source travels in both directions to all all the
machines connected to bus cable until it reaches intended receipt.
 Advantage – Its economical; Disadvantage – If Backbone breaks
whole network will shutdown.

11. S TA R N E T WO R K
 In star network each network host is connected to a central hub
with a point-to-point connection.
 The hub is the server and peripherals are the client.
 All the data on the star topology passes through the central
device before reaching the intended destination.
 Advantage - Reliable; Disadvantage – Expensive to install

13. R I N G N E T WO R K
 In Ring Topology, all the nodes are connected to each-other in such a
way that they make a closed loop.
 Each workstation is connected to two other components on either
side, and it communicates with these two adjacent neighbors.
 Data travels around the network, in one direction. Sending and
receiving of data takes place by the help of TOKEN.
 Advantage – Less wiring; Disadvantage – Very slow


15. T R E E N E T WO R K
 Tree Topology integrates the characteristics of Star and Bus
Topology.
 In Tree Topology, the number of Star networks are connected using
Bus. This main cable seems like a main stem of a tree, and other star
networks as the branches. It is also called Expanded Star Topology.
Advantage – Its big; Disadvantage - Not reliable

17. MESH NETWORK
 In Mesh Network each node, computer and other devices are interconnected
to each other.
 Every node not only sends its own signals but also relays data from other
nodes.
 This type of topology is very expensive as there are many redundant
connections, thus it is not mostly used in computer networks. It is commonly
used in wireless networks.
Advantage – Traffic abundance; Disadvantage – Highly expensive

19. COMPUTER COMPONENTS

20. Input Devices:1. Mouse (Pointer Device)
2. Keyboard
3. Joystick
4. Scanner
5. Microphone
6. Webcam

22. Central Processing Unit:
1. Processor (CPU)

23. Output Devices:1. Monitor (Screen)
2. Printers
3. Speakers

25. Storage Devices:1. ROM (Random Access Memory)
2. ROM (Read Only Memory)
3. Hard Disks (Read/Write)
4. CD/DVD Drives

27. NETWORK COMPONENTS
 Network interference card - is found in the circuit board or mother board. It
helps devices to connect to a network.
 Network software - is software designed to manage a network.
 Network cable/wire - Used to connect devices together to form a network.
 Hub- Central device used in Star Networks which is not reliable and is slow.
 Switch- Central device used in Star Network which is safe
 Router – A device which forwards data packets to the appropriate computer
network.

29. INTERNET SECURITY
The Need Of Internet Security:1. It is protection against viruses, malware etc. even hackers.
2. Commercial & Government Enterprises are reluctant to use the
Internet because of security concerns. Since Internet ultimately
connects to a public network, the security concerns are very much valid.
3. The need for security is being alarmingly realized with the emergence of
E-Commerce. Presently, E-Commerce operations are always threatened
by fear of loss of money and privacy.

30. 3.
Governments, military, corporations, financial
institutions, hospitals, and private businesses amass a
great deal of confidential information about their
employees, customers, products, research and financial
status. Most of this information is now collected,
processed and stored on electronic computers and
transmitted across networks to other computers.
4. Even E-mail is also under threat. When sent across the
Internet, the E-mail can be intercepted and read by
anybody who can lay his hands on it.

31.  If you are planning to connect your organization to Internet
and your computers are accessed from remote places, you must
have a Firewall to protect your Intranet.
 Firewall is defined as a group of systems that enforce an access
control policy between two networks. In other words it is a
mechanism used to protect trusted network from an untrusted
network.
 Firewall acts as a Gatekeeper between a company’s internal
network and the outside world. It acts as an electronic barrier to
stop unauthorized entry.

33. A Firewall Performs Two Basic Functions: 1. Gatekeeping - It examines the location from which the
data enters your system and then decides based on your
instructions whether or not to allow the information.
2. Monitoring - It includes login of all system activities
and generation of reports for system administration.
Monitoring can be active or passive. In active
monitoring a firewall notifies a manager whenever an
incidence occurs, generally by E-mail or Pager. In
passive monitoring the manager has to go through the
logs to determine and analyze the system activities.

34. Draw Backs Of Firewall:1. An Internet Firewall cannot protect against attacks that do not go through
the Firewall. For example, if an unrestricted dial-out connection is
permitted from inside the protected network the users can make a direct
connection to the Internet. Users who become irritated with the additional
authentication required by the Firewall may temp to bypass the security
system by purchasing a direct connection to an ISP.
2. The Internet Firewall cannot protect against threats posed by traitors who
may copy sensitive data into floppies and other media. A hacker may also
persuade someone to reveal a password and grant him a temporary network
access. Hence, there is a need to periodically change the passwords.
3. The Firewall Cannot Protect Against The Transfer Of Virus Infected Files
Or Software. Hence, Anti-Viral Software Should Be Deployed At Each
Desktop.
4. Lastly the Internet Firewall cannot protect against data driven attacks. A
data driven attacks occur when seemingly harmless data is mailed or copied
to a computer and executed to launch a hidden attack.

35. MALWARE’S
 Malware, short for malicious software, is software used to disrupt
computer operation, gather sensitive information, or gain access to
private computer systems.
 Malware includes computer viruses, ransomware, worms, trojan
horses, rootkits, keyloggers, dialers, spyware, adware,
malicious BHOs, rogue security software and other malicious programs.

36. MAIN TYPES OF
MALWARE’S
1. Virus
2. Trojan Horse
3. Spyware
4. Worm
5. Adware

37. VIRUS
 Viruses are programs that can replicate their structures of effects
by inflecting other structures on a computer. The common use of
virus is to take over a computer to steal data.

38. TROJAN HORSE
 A destructive program that masquerades as a being application.
Unlike viruses, Trojan horses do not replicate themselves but they can
be just as destructive. One of the most insidious types of Trojan
horse is a program that claims to rid your computer of viruses but
instead introduces viruses onto your computer.

39. SPYWARE
 Spyware is a type of malware that is installed on a computer
without the knowledge of the owner in order to collect the owner’s
private information. Spyware is often hidden from the user in order to
gather information about internet interaction, keystrokes (also known
as key logging), passwords, and other valuable data.

40. WORM
 A program that makes copies of itself; for example, from one disk
drive to another, or by copying itself using email or another transport
mechanism. The worm may do damage and compromise the security
of the computer. It may arrive in the form of a joke program or
software of some sort.

41. ADWARE
 Adware, or advertising-supported software, is any software package
which automatically renders advertisements in order to generate revenue
for its author. The advertisements may be in the user interface of the
software or on a screen presented to the user during the installation
process. The functions may be designed to analyze which Internet sites
the user visits and to present advertising pertinent to the types of goods
or services featured there. The term is sometimes used to refer to
software that displays unwanted advertisements.

42. ANTI-VIRUS
 It is software used to detect and remove the malicious software/file,
such as: computer viruses, malicious BHOs, hijackers,
ransomware, keyloggers, backdoors, rootkits, trojan horses, worms,
malicious LSPs, dialers, fraudtools, adware and spyware.
 No matter how useful antivirus software can be, it can sometimes have
drawbacks. Antivirus software can impair a computer's performance.
 Inexperienced users may also have problems understanding the
prompts and decisions that antivirus software presents them with.

43. EXAMPLES OF ANTIVIRUS

44. CIA
 The CIA triad (confidentiality, integrity and availability) is one of
the core principles of information security.
 CIA is a widely used benchmark for evaluation of information
systems security, focusing on the three core goals
of Confidentiality, Integrity and Availability of information.
 It is designed to guide polices for information security within an
organization.

45. CONFIDENTIALITY
 Confidentiality refers to limiting information access to authorized
users and preventing access by unauthorized users.
 The information in today’s time is very valuable. Bank account
statements, personal information, credit card numbers, trade secrets,
government documents. Every one has information they wish to keep a
secret. Protecting such information is a very major part of information
security.

46.  A very key component of protecting information confidentiality would be
encryption. Encryption ensures that only the right user) can read the
information. Encryption is VERY widespread in today’s environment and
can be found in almost every major protocol in use. A very prominent
example will be SSL/TLS, a security protocol for communications over the
internet that has been used in conjunction with a large number of internet
protocols to ensure security.
 Other ways to ensure information confidentiality include enforcing file
permissions and access control list to restrict access to sensitive
information.

47. INTEGRITY
 Integrity of information refers to protecting information from
being modified by unauthorized users.
 Information only has value if it is correct. Information that has
been tampered with could prove costly. For example, if you were
sending an online money transfer for $100, but the information was
tampered in such a way that you actually sent $10,000, it could prove to
be very costly for you.

48.  As with data confidentiality, cryptography plays a very major role in
ensuring data integrity. Commonly used methods to protect data integrity
includes hashing the data you receive and comparing it with the hash of the
original message. However, this means that the hash of the original data
must be provided to you in a secure fashion. More convenient methods
would be to use existing schemes such as GPG to digitally sign the data.

49. AVAILABILITY
 Availability of information refers to ensuring that authorized users are able
to access the information when needed.
 Information only has value if the right people can access it at the right
times. Denying access to information has become a very common attack
nowadays. Almost every week you can find news about high profile websites
being taken down by DDOS attacks. The primary aim of DDOS attacks is to
deny users of the website access to the resources of the website. Such
downtime can be very costly. Other factors that could lead to lack of
availability to important information may include accidents such as power
outages or natural disasters such as floods.

50.  How can one ensure data availability? Backup is key. Regularly doing
backups can limit the damage caused hard drives or natural disasters. For
information services that is highly critical, redundancy might be
appropriate. Having a off-site location ready to restore services in case
anything happens to your primary data centers will heavily reduce the
downtime in case of anything happens.

51. SOURCES: Wikipedia.org
 Ianswer4u.com
 Computernetworking.about.com
 Googleimages.com
 http://it.med.miami.edu/x904.xml
 Information Technology Book