Chapter 3

Computer Communication and Security

Chapter 3 Objectives

Communications and Network

terminology and applications

Various communications devices, media, and procedures

Type of Computer Networks

Describe the types of computer-

network & Internet security risks

Identify ways to safeguard against Network-based

attacks

Techniques to prevent Network

Attacks

Communications

• What are computer communications? • Process in which two or more computers or devices transfer data, instructions, and

information

Communications

• What is needed for successful communications?

• Initiates instruction to transmit data, instructions, or information. Commonly in software forms

Sending device

• Connects the sending device to the communications channel

Communications device

• Media on which data, instructions, or information travel

Communications channel

• Connects the communications channel to the receiving device

Communications device

• Accepts transmission of data, instructions, or information

Receiving device

Communication Software

• What is communications software?

Programs that help users establish connection to Internet, other network, or another computer Programs that help users

manage transmission of data, instructions, and information

Programs that provide an interface for users to communicate with one another

Communication Devices

• What are examples of communications devices?

Common types are [dial-up modems, ISDN & DSL modems, broadband/cable modems] For

Internet Communication, and [network cards, wireless access points, routers, and

hub/switches] for General Computer Network Communications

Communication Devices

• What is a modem? • Converts digital signals to analog signals and vice versa

• Notebook computers often use PC Card modem

Dial Up Modems

Cable and Wireless Broadband Modems Faster Internet Connection

Communications Devices

• What is a network card?

– Adapter card, PC Card, or compact flash card that enables computer or device to access network

– Sometimes called network interface card (NIC)

Communications Devices

• What is a wireless access point?

– Central communications device that allows computers and devices to transfer data wirelessly among themselves or to wired network

Communications Devices

• What is a router?

– Connects computers and transmits data to correct destination on network

– Routers forward data on Internet using fastest available path

Communications Devices

Communications Devices

• What is a switch/hub?

– Device that provides central point for cables in network

Communications Channel

• What is a channel?

– Transmission media on which data travels in communications system

Transmission media

are materials capable of carrying one or more signals

Bandwidth is amount of data that can travel over channel

Transmission Media

Physical

• Optical Fiber

• Twisted Pair Cables

• Coaxial Cable

Wireless

• Communications Sattelite

• Microwave Radio

• Cellular Radio (2G, 2,5G, 3G, etc)

• Broadcast Radio (Wi-fi, Bluetooth)

• Infrared

Computer Network

• What is a network? – Collection of computers

and devices connected via communications devices and transmission media

Computer Network

• What is a local area network (LAN)? – Network in limited

geographical area such as home or office building

– Metropolitan area network (MAN) connects LANs in city or town

Computer Network

• How to Join a computer into a LAN

IP address is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network

Computer Network

• What is a wide area network (WAN)? – Network that covers

large geographic area using many types of media

– Internet is world’s largest WAN

Computer Network

• What is a client/server network? – One or more computers act

as server and other computers, or clients, access server

Computer Network

• What is an Intranet?

Internal network that uses Internet technologies

Makes information accessible to employees

Typically includes connection to Internet

Extranet allows customers or suppliers to access part of company’s intranet

Network Risks & Security

Computer Security Risks

• What is a computer security risk?

– Action that causes loss of or damage to computer system

– Mostly happened when computer connected into a network

• Easier to access, more unpredictable than attacking unattended computer

Computer Viruses, Worms, and Trojan Horses

• What are viruses, worms, and Trojan horses?

Virus is a potentially damaging computer program

Worm copies itself repeatedly,

using up resources

and possibly shutting down computer or

network

Trojan horse hides within

or looks like legitimate program

until triggered

Payload (destructive

event) that is delivered when

you open file, run infected program, or boot computer with

infected disk in disk drive Can spread

and damage

files

Does not replicate itself on

other computers

• How can a virus spread through an e-mail message?

Step 1. Unscrupulous

programmers create a virus

program. They hide the

virus in a Word document

and attach the Word

document to an e-mail

message.

Step 2. They use

the Internet to send

the e-mail message

to thousands of

users around the

world.

Step 3b. Other users do not

recognize the name of the

sender of the e-mail message.

These users do not open the

e-mail message. Instead they

delete the e-mail message.

These users’ computers are not

infected with the virus.

Step 3a. Some

users open the

attachment and

their computers

become infected

with the virus.

Computer Viruses, Worms, and Trojan Horses

• What are some tips for preventing virus, worm, and Trojan horse infections?

Install a personal firewall program

If the antivirus program flags an

e-mail attachment as infected, delete

the attachment immediately

Never download or install suspicious

software from untrusted sources

Never open an e-mail attachment

unless you are expecting it and

it is from a trusted source

Install an antivirus program on all of your

computers

Check all downloaded programs for

viruses, worms, or Trojan horses

Computer Viruses, Worms, and Trojan Horses

DOS & Backdoor

• What is a denial of service (DOS) attack and back door?

A denial of service attack is an assault which disrupts computer access to an Internet service

such as the Web or e-mail

A back door is a program or set of instructions in a program that allow users to bypass

security controls when accessing a computer resource

Spoofing

• What is spoofing?

Makes a network

or Internet Transmission appear legitimate

IP spoofing occurs when an intruder computer fools a network into believing

its IP address is from a trusted source

Perpetrators of IP spoofing trick their victims into interacting

with a phony Web site

Solutions

• Best way to prevent spoofing and DOS is to build a firewall

– Implemented on network or installed on host as

software (personal firewall)

Solutions

• What is firewall?

– Security system consisting of hardware and/or software that prevents unauthorized intrusion

Solutions

• What is personal firewall? – Program that protects personal computer and its data from

unauthorized intrusions

– Monitors transmissions to and from computer

– Informs you of attempted intrusion

Unauthorized Access and Use

• Unauthorized Access – Use of a computer or network without

permission.

– By connecting to it and then logging in as a legitimate user.

– Do not cause damages.

– Merely access the data, valuable information or programs in the computer.

– In some manners, can be categorized as Information theft

• Unauthorized Use

– Use of a computer or its data for unapproved or illegal activities.

– Ex: gaining access to a bank computer and performing an unauthorized bank transfer etc.

Unauthorized Access and Use

Solutions

• How to prevent unauthorized access and use?

– Make a good use of authorization control

Solutions (Cont.)

• How to make good passwords?

GOOD

• Example: @k|_|-@n@6-4L4Y

• Longer, alay-er, better

NEVER USE IT

• Your birth-day • Your mother/dad/lover name • Very predictable words • Plain, not combinated

characters is weak against brute-force attacks

Solutions (Cont.)

• How to prevent unauthorized access and use?

– Disable file and printer sharing on Internet connection

– enable just when you need it

File and printer sharing

turned off

Solutions (Cont.)

• How to make information thief life’s much harder?

– Use encryption

• Safeguards against information theft

• Process of converting plaintext (readable data) into ciphertext (unreadable characters)

• Use key to generate cipherkey as combinations

• To read the data, the recipient must decrypt, or decipher, the data

• See the demonstration

Internet Security Risk

• Information Sniffing, How?

• H or L can get all sensitive un-encrypted information passed on network such as username and password

Username, Passwords, Credit card’s details

Internet Security Risk

• Website phising, How?

https://ib.bankmandiri.co.id/retail/Login.do?action=form https://ib.bangmandiri.co.id/retail/Login.do?action=form

Impersonated Login Page

Bank Mandiri’s Server

Username, Passwords, Credit card’s details

Cracker’s Computer

Normal Login Page

Internet Security Risk

• Website phising commonly spread using emails and social media

• Best implemented when combined with social engineering technique.

Internet Security Risk

• Social engineering is an non-technical, outside hacker's use of psychological tricks on legitimate users of a computer system, in order to gain the information (usernames and passwords) one needs to gain access to the system.

• It utilizes two human weakness:

– no one wants to be considered ignorant

– human trust

Solutions

• Web browsers provide secure data transmission

Many Web browsers use encryption

Secure site Choose Web site that

uses encryption to secure data

Valid Digital certificate

Guarantees Web site is legitimate

Solutions

• Provides encryption of all data that passes between client and Internet server

– Web addresses beginning with “https” indicate secure connections

Solutions

• Protect yourselves from social engineering

– Be educated, aware, and a little bit paranoid.

– Never give out:

• Usernames / ID numbers

• Passwords / PIN numbers

• System information

• Credit card numbers

• Schedules

• Other Sensitive data

– Be aware of what is being asked

End of Chapter 3