What we will learn today: Security Communication

What we will learn today:

Security Communication

What are the main safety and security issues when using computers? How can data/files be kept safe?

10 Security

000-209 Intro to CS. 9/Secure

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Overview

1. Hardware Reliability 2. Backing up your Data 3. Computer Viruses 4. Keeping Data Safe 5. Internet Security


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The reliability of a computer component is measured in MTBF (mean time between failures). hardware is tested in a laboratory number of failures is divided by total hours of

observation

It’s better to plan for a hardware failure than hope one doesn’t happen.

1. Hardware Reliability


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Downtime - time when a computer is not functioning.

Hardware redundancy (maintaining extra equipment) is a popular safeguard used by e-commerce sites.

Hardware Failure


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A power failure is a complete loss of power to the computer system. data stored in RAM will be lost

A power spike is a brief increase in power less than one-millionth of a second

A power surge lasts a little longer

Surges and spikes can damage computers.

Power Supply Problems


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A UPS (uninterruptible power supply) is the best protection against power failures, surges, and spikes.

A UPS contains a batterythat keeps your computerrunning for several minutesduring a power failure

Uninterruptible Power Supply


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A surge strip can protect your computer and other devices from power spikes and surges. does not contain a battery

Surge protector vs. Power strips

continued


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Don’t mistake a power strip for a surge strip a power strip provides multiple outlets but cannot

protect your computer from power spikes and surges


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Copying files, or the contents of am entire disk, provides the best security for your data.

Backup tips: scan for viruses before backing up make frequent backups (once a day/week) check the backups store backups away from your computer

2. Backing up your Data


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Consider capacity, speed, and reliability.

What to Use for Backups


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Backup Software

Norton Ghost 9.0Simply Safe Backup (free)

http://www.simplysafebackup.com/


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Use Northern Ghost 8

It is old version, but less than 1.4 MB can run in one floppy disk. It runs under DOS can be used to back up: One disk to another disk, one partition to another partition (usually,

Driver C, to Driver D under one disk)


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Types of Backups

Full backup copy all the files safe but can take a long time

Differential backup copy the files that have changed since the last full backup takes less time but more complex

Incremental backup copy the files that have changed since the last backup


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A computer virus is a program that attaches itself to a file, duplicates itself, and spreads to other files.

3. Computer Viruses


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The following signs might mean that your computer has a virus: displays a rude, embarrassing message unusual visual or sound effects difficulty saving files files mysteriously disappear the computer works very slowly applications increase in size for no reason

Virus Warning Signs


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A boot sector virus infects the system files that your computer uses.

A macro virus infects a macro. Macros are tiny programs used in word

documents, databases, spreadsheets, and many other large applications

Virus Types


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Macro viruses are the most common.

Most Popular Virus Types


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Do not get files from high risk sources Use anti-virus software

Computer Protection


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Don't: E-mail any attachments from your machine Ignore it, hoping it will go away

Do: tell your system administrator remove it using anti-virus software keep anti-virus software updated

When a Virus Hits...


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Anti-virus software

avast! Home Edition (free)http://www.avast.com/

Norton AntiVirus


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Anti-virus software checks for a virus signature – a unique series of bytes that identifies a known virus inside another program.

Hackers keep making new viruses, with new signatures, so anti-virus software needs to be updated regularly. usually automatically via the Internet

Virus Detection Methods


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A Trojan horse is a computer program that appears to do something good/useful while actually doing something bad. not a virus, but may carry a virus does not duplicate itself

Example: a free game available for download from an unknown Web site it really deletes files once it is started

A Trojan Horse


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A time bomb is a program that stays in your system undetected until it is triggered by a certain event in time. e.g. on "Friday 13th" it deletes all your files usually carried as a virus or in a Trojan horse

A Logic bomb is a program triggered by changes to your files. e.g. every new Word file is deleted

Bombs


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A software worm is a program designed to enter a computer system through security holes in the computer network.

Worms


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Good habits: save files frequently when you are working on them backup files frequently use anti-virus software do not open documents with unknown macros

4. Keeping Data Safe


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Acceptable use policy - rules that specify how a computer system should be used determined by management used by large organizations makes users aware of limits and penalties provides framework for legal action

Acceptable Use Policy


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User rights - rules that limit directories and files that each user can access. erase rights create rights write rights read rights file find rights

User Rights


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Keep data backups in a locked room, away from the main computing area.

Offices with computers should be locked when there is no one around.

Computers can be chained to their desks.

Restrict Physical Access


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Personal identification help identify authorized users: identity badges user IDs and passwords biometrics

Personal IDs


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Fingerprint scanners canconfirm your identityin less than two seconds.

Biometric Example


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Scramble information so it cannot be understood until it is decrypted.

Encryption


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Many Internet security problems are due to ActiveX controls developed by Microsoft to extend the power of

Internet Explorer

ActiveX controls can be part of Web pages downloaded by Internet Explorer

5. Internet Security and ActiveX

continued


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ActiveX controls has full access to your computer. hackers can use ActiveX controls to cause havoc

Digital certificates identify the author of an ActiveX control controls with digital certificates should be safe, if you

trust the certificate!

Internet Explorer can be configured to reject all ActiveX controls that do not come with certificates.


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Most e-commerce sites provide a secure channel for transmitting credit card data.

SSL (Secure Socket Layers) uses encryption to establish a secure connection. SSL pages start with https instead of http.

S-HTTP encrypts data one message at a time.

Electronic Commerce Security

continued


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Encrypted messages ensure that credit card numbers cannot be intercepted between a computer and an e-commerce site.

During securetransactions, Internet Explorerdisplays a lockicon and Netscape Navigator displaysa key icon.

We look at the basic elements of a communications systems, and the various services available.

Communications

000-209 Intro to CS. 11/Comm. Systems

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Overview

1. What is a Communications System? 2. Bandwidth 3. Network Topology 4. Protocols 5. Packet Switching 6. Circuit Switching 7. Analog <-> Digital Conversion 8. Telephone Services 9. Cable-based Services 10. Wireless


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A communications system is a combination of hardware, software, and connecting links that transport data between a sender and a receiver.

A sender and receiver are linked by a communications channel e.g. telephone lines,

fiber-optic cable

1. What is a Communications System?


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The amount of data that can be sent over a network in a certain period of time.

Usually measured in bits per second (bps), kilobits per second (kbps), or megabits per second (mps).

Two main types: broadband (high capacity)

e.g. by using fibre-optic cable

narrowband (less capacity)e.g when using the telephone system

2. Bandwidth


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The shape of the interconnections in a communications system is its topology.

Star topology - the communications lines fan out from a central location every connection is dedicated to one user

3. Network Topology

continued


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A bus topology provides a common or shared communications link used by cable TV companies

continued


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A ring topology connects devices in a continuous loop used by older local area networks


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A communications protocol is a set of rules about how a sender and receiver should communicate.

The rules specify such things as data representation, signalling, authentication, and er

ror detection

4. Protocols


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5. Packet Switching

Data is separated into small packets.

Each packet is sent through the network using the best route available at that time.

At the receiving end, the packets are reassembled into the original data.

Packet switching is used by the Internet.

continued


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1. A message is divided into packets.

2. Each packet is addressed to its destination.

3. A packet might travel the shortest path to its destination.

4. If a route is congested or

inoperable, packets can be rerouted to

other links.

5. When the packets arrive at their destination, they are reassembled.


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Advantages of Packet Switching

Packet switching uses network bandwidth efficently.

It minimizes transmission latency the time it takes for data to pass across the network

Packet switching can deal with network failure.


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A dedicated communications path is established between two devices through one or more switching nodes.

Unlike packet switching, digital data is sent as a continuous stream of bits.

The telephone system uses circuit switching.

6. Circuit Switching


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Advantages of Circuit Switching

Bandwidth is guaranteed.

Any communication delay is only due to propagation time.

Primary advantage of the telephone system for computer communications is that it's cheap for users.


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Telephone systems use miles and miles of twisted-pair cables.

Twisted-pair cableterminates with a plastic RJ-45connector.

Twisted Pair Cable


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Old phone lines use analog sound signals. Modern systems use digital signals:

less susceptible to noise require simpler circuitry

It's possible to convert analog signals into digital signals (and vice versa).

7. Analog <-> Digital Conversion


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Analog and Digital Signals


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The Conversion Process

Transmission to neighborhoodSwitch box (within 1800 yards)

Neighborhood switchMay convert to digital. May remain analog Transmission to city

Point of Presence central switch

Central office PoPDefinitely digital now

National Backbone,All digital networks

Central office PoP - incoming digital may be converted to analog

Neighborhood switchIf not analog already, converted at this point

Modem in computerConverts analog to digital

Transmission to neighborhoodswitch box(within 1800 yards)


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POTS (plain old telephone service) is an analog service.

Voiceband modem - converts digital pulses into analog tones to send digital computer data over a POTS line.

8. Telephone-based Services

continued


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ISDN a standard for digital transmission of voice and

data uses circuit switching with ordinary telephone w

ire (and other media, such as fibre-optic cable) it requires hardware adapters at both ends of the

transmission basic (64 kbps); enhanced (128 kbps)

continued


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ADSL (Asymmetric Digital Subscriber Line) for transmitting digital information at a high bandwidt

h on existing phone lines

ADSL offers asymmetric data rates 1.5 to 9 Mbps when receiving (the downstream rate) 16 to 640 Kbps when sending (the upstream rate)

Speeds depends on distance from the telephone company office at most ~3 miles away continued


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T1 Line - provides 1.544 Mbps send and receive capacity over a dedicated line

T3 Line - uses fiber-optic cables to provide service with a capacity of 44.736 Mbps the equivalent of 28 T1 lines enough to show full-screen, full-motion video


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Fiber-optic cable is a bundle of extremely small tubes of glass called optical fibers. thinner than human hair

Fiber-optic cable is replacing twisted-pair cable where high bandwidth is required

Fiber-Optic Cable

continued


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How fiber-optic cable works: miniature lasers send pulses of light each fiber is a one-way communications

channel light signals encounter little resistance


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Cable TV companies in the US have installed miles of high-bandwidth coaxial cables. carrying capacity far in excess of POTS lines

A cable modem is a device designed to demodulate a signal from the cable and translate it back into Internet data.

9. Cable TV-based Services


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Coaxial cable - high-capacity communications cable consisting of a copper wire conductor common use is to carry television signals

Coaxial cablecontains shieldingwhich increasesbandwidth.

Coaxial Cable

continued


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Coaxial cable: has excellent bandwidth, but not as good as

fibre-optic cable more expensive more difficult to work with than twisted-pair


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Radio-based systems that allow transmission of information without a physical connection, no need for copper wire or fiber-optic

Cellular, infrared, microwave, and satellite broadcasting are forms of wireless communication.

Common wireless standards include 802.11b, and Bluetooth.

10. Wireless Communications


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Infrared transmissions occur below the visible light of spectrum. requires line-of-sight communication

sender must be able to see the receiver

Infrared Wireless


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High-frequency radio waves used for point-to-point and one-directional communication of audio and data.

Requires line-of-sight, and ground stations must be within 30 miles of each other.

Many communications systems transmit microwave signals between a land-based ground station and a satellite.

Microwaves


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Direct satellite service (DSS) uses a geosynchronous or low-earth orbit satellite to send television, voice or computer data directly to a satellite dish. transmits in one direction – downstream requires a standard modem and phone line for

upstream transmission

Satellite


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801.11

802.11 is a family of specifications developed by the IEEE for wireless communications. IEEE = Institute of Electrical and Electronics Enginee

rs

802.11b: provide data rates of up to 11 Mbps per second at distances up to approximately 300 feet. also called Wi-Fi line-of-sight not required


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Bluetooth

An open standard for short-range (30 feet) and low speed (up to 1Mbps) wireless transmission of digital voice and data. line-of-sight not required low-power (unlike 802.11b), so suitable for portable d

evices


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Review for Final Exam

1. Read the following three notes:

07.files04.

08IntroductionLinuxOS.pdf

12security09.ppt


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2. Explain the following in essay form. Give your own opinion on the subject.

What is Linux? Describe your experience with any Linux Distro you have used?

Based on your computer skill and knowledge, provide a solution how to prevent computer virus.

As a Buddhist, what are ethical practices in the use of computers? Discuss.

Documents

What we will learn today: Security Communication