Networking & Security

COMPUTER NETWORK

CONTENTS

What is a computer network?

Types of network

Network topologies

Computer components

Network components

Internet security

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.

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.

TYPES OF NETWORK

Main Types Of Network:- 1. PAN (Personal Area Network)2. LAN (Local Area Network)3. WAN (Wide Area Network)4. MAN (Metropolitan Area Network)

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.

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

BUS NETWORK

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.

STAR NETWORK

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

RING NETWORK

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

TREE NETWORK

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

MESH NETWORKIn 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

COMPUTER COMPONENTS

Input Devices:-

1.Mouse (Pointer Device)

2.Keyboard

3.Joystick

4.Scanner

5.Microphone

6.Webcam

Central Processing Unit:1. Processor (CPU)

Output Devices:-

1.Monitor (Screen)

2.Printers

3.Speakers

Storage Devices:-

1.ROM (Random Access Memory)

2.ROM (Read Only Memory)

3.Hard Disks (Read/Write)

4.CD/DVD Drives

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.

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.

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.

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.

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.

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.

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.

MAIN TYPES OF MALWARE’S

1.Virus

2.Trojan Horse

3.Spyware

4.Worm

5.Adware

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.

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.

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.

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.

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.

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.

EXAMPLES OF ANTIVIRUS

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.

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.

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.

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.

INTEGRITY

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.

AVAILABILITYAvailability 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.

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.

SOURCES:-

Wikipedia.org

Ianswer4u.com

Computernetworking.about.com

Googleimages.com

http://it.med.miami.edu/x904.xml

Information Technology Book

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Made By:-SukrantGrade - 9