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Chapter 7Chapter 7

Networking and Security:Networking and Security:Connecting Computers and KeepingConnecting Computers and Keeping

Them Safe from Hackers and VirusesThem Safe from Hackers and Viruses

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Chapter TopicsChapter Topics

•• Networking fundamentalsNetworking fundamentals•• Network architectureNetwork architecture•• Network componentsNetwork components•• Peer-to-peer networksPeer-to-peer networks•• Ethernet networksEthernet networks•• Computer threatsComputer threats•• Computer safeguardsComputer safeguards•• Computer virusesComputer viruses

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Networking FundamentalsNetworking Fundamentals•• Computer network:Computer network:

–– Two or more computers connected togetherTwo or more computers connected together–– Devices connected to networks: nodesDevices connected to networks: nodes

•• Benefits of a network:Benefits of a network:–– Sharing resourcesSharing resources–– Transferring filesTransferring files

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Network ArchitectureNetwork Architecture

•• Network designs:Network designs:–– Locally administered:Locally administered:

•• Peer-to-peer (P2P)Peer-to-peer (P2P)–– Centrally administered:Centrally administered:

•• Client/serverClient/server

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Peer-to-Peer NetworksPeer-to-Peer Networks

•• Nodes communicateNodes communicatewith each other:with each other:–– PeersPeers

•• Share peripheralShare peripheraldevicesdevices

•• Used in home andUsed in home andsmall office networkssmall office networks

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Client/Server NetworksClient/Server Networks

•• Client computers:Client computers:–– Users who makeUsers who make

requestsrequests•• Server computers:Server computers:

–– Provide resources toProvide resources toclientsclients

–– Central network controlCentral network control•• InternetInternet

–– A large, A large, multiservermultiserver,, multiclient multiclient network.network.

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LANs and WANsLANs and WANs

•• Local area network (LAN):Local area network (LAN):–– Nodes are within a small geographic region:Nodes are within a small geographic region:

•• HomesHomes•• SchoolsSchools•• Small businessesSmall businesses

•• Wide area network (WAN):Wide area network (WAN):–– LANs connected over long distances:LANs connected over long distances:

•• A few miles to thousands of milesA few miles to thousands of miles•• Use telecommunications linesUse telecommunications lines

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Network ComponentsNetwork Components•• Transmission mediaTransmission media•• Network communicationNetwork communication

devicesdevices•• SoftwareSoftware

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Transmission MediaTransmission Media•• Provides communications channel betweenProvides communications channel between

nodesnodes•• Forms of media:Forms of media:

–– Twisted pairTwisted pair–– Coaxial cableCoaxial cable–– Fiber-optic cableFiber-optic cable–– Radio waves:Radio waves:

•• WirelessWireless

•• Bandwidth:Bandwidth:–– Data transfer rateData transfer rate–– ThroughputThroughput

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Network AdaptersNetwork Adapters

•• Devices connected to or installed in nodes:Devices connected to or installed in nodes:–– Network interface cards (Network interface cards (NICsNICs))–– External network adaptersExternal network adapters

•• Enable communication between nodesEnable communication between nodes

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Network Navigation DevicesNetwork Navigation Devices•• Devices that help make data flow possibleDevices that help make data flow possible•• Routers:Routers:

–– Route data between networksRoute data between networks•• Switches:Switches:

–– Receive data and retransmit it to nodes on theReceive data and retransmit it to nodes on thesame networksame network

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Networking SoftwareNetworking Software•• Peer-to-Peer SoftwarePeer-to-Peer Software

•• Built into operating systems that supportBuilt into operating systems that supportnetworkingnetworking

–– WindowsWindows–– Mac OSMac OS

•• Client/Server SoftwareClient/Server Software•• Network operating system (NOS) softwareNetwork operating system (NOS) software

–– Windows XP ProfessionalWindows XP Professional–– Windows Server 2003Windows Server 2003–– Novell NetwareNovell Netware–– Windows Vista EnterpriseWindows Vista Enterprise

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Types of Peer-to-Peer NetworksTypes of Peer-to-Peer Networks

•• Wired Ethernet networksWired Ethernet networks•• Wireless Ethernet networksWireless Ethernet networks•• Power-line networksPower-line networks

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Wired Ethernet NetworksWired Ethernet Networks

•• Ethernet networkEthernet networkadapters are used toadapters are used toconnect nodesconnect nodes–– NIC cardNIC card–– PC CardPC Card–– USB adapterUSB adapter

•• Computers areComputers areconnected to eachconnected to eachother using unshieldedother using unshieldedtwisted pair cabletwisted pair cable

Ethernet

Phone

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Ethernet SwitchesEthernet Switches

•• Keep track of data packetsKeep track of data packets•• Amplify and retransmit signalsAmplify and retransmit signals•• Keep the network running efficientlyKeep the network running efficiently

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Ethernet RoutersEthernet Routers

•• Transfer packets from one network to anotherTransfer packets from one network to another•• Home Internet routers transfer data from theHome Internet routers transfer data from the

Internet to the home network.Internet to the home network.

Router

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Wireless Ethernet NetworksWireless Ethernet Networks

•• Uses radio waves to connect nodesUses radio waves to connect nodes•• Basically an Ethernet network that uses radioBasically an Ethernet network that uses radio

waves instead of wireswaves instead of wires•• Each node requires a wirelessEach node requires a wireless network adapter:network adapter:

–– TransceiversTransceivers

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Power-Line NetworksPower-Line Networks

•• Computers areComputers areconnected to aconnected to ahousehouse’’s electricals electricalwiring to create awiring to create anetworknetwork

•• Power-line networkPower-line networkadapter is used toadapter is used toconnect nodes toconnect nodes toelectrical outletselectrical outlets

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Choosing a Peer-to-PeerChoosing a Peer-to-PeerNetworkNetwork

•• Things to consider:Things to consider:- - Whether you want wireless communicationsWhether you want wireless communications- - How fast you want your network connection to beHow fast you want your network connection to be- - Whether existing wiring is availableWhether existing wiring is available- How much money you can spend on your network

$$$$$$$Relative installationand equipment costsfor networkingtwo computers

100 to 630bps

108 Mbps54 Mbps100 Mbps to1,000 bps (1 gigabit)

Maximum dataTransfer rate(bandwidth)

Wireless802.11n

WirelessEnhanced G

Wireless802.11g

WiredEthernet

Comparing the Major Types of Home Networks

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Configuring SoftwareConfiguring Softwarefor a Home Networkfor a Home Network

•• WindowsWindows–– Windows Vista home versionsWindows Vista home versions

•• Network setup wizard Network setup wizard–– Wired or wirelessWired or wireless

–– Windows XPWindows XP•• Network setup wizardNetwork setup wizard

–– Windows 98Windows 98•• Configure manuallyConfigure manually

–– Help has a clear instructionHelp has a clear instruction

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Computer ThreatsComputer Threats•• Cybercrimes Cybercrimes are criminal acts conducted throughare criminal acts conducted through

the use of computers by the use of computers by cybercriminalscybercriminals..

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HackersHackers

•• Anyone who unlawfully accesses aAnyone who unlawfully accesses acomputer systemcomputer system

•• Types of hackers:Types of hackers:–– White-hatWhite-hat–– Black-hatBlack-hat–– Script kiddiesScript kiddies

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What Hackers DoWhat Hackers Do

•• Steal information from computers:Steal information from computers:–– Credit card numbersCredit card numbers–– Bank account numbersBank account numbers

•• Internet packet sniffingInternet packet sniffing•• Commit identity theftCommit identity theft

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How Computers Are AttackedHow Computers Are Attacked

•• Trojan horseTrojan horse•• BackdoorBackdoor

programprogram–– ZombiesZombies

•• Denial ofDenial ofservice attacksservice attacks

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How Hackers Gain AccessHow Hackers Gain Access

•• Direct access:Direct access:–– Hacking softwareHacking software

•• Indirect access:Indirect access:–– Internet connectionInternet connection–– Logical portsLogical ports

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Computer Safeguards:Computer Safeguards:FirewallsFirewalls

•• Software programs or hardwareSoftware programs or hardwaredesigned to close logical ports todesigned to close logical ports toinvadersinvaders–– A firewall is built into Windows VistaA firewall is built into Windows Vista–– More robust firewalls are available fromMore robust firewalls are available from

other vendorsother vendors–– Firewalls are critical if you have an always-Firewalls are critical if you have an always-

on broadband connectionon broadband connection

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Protecting a Wireless NetworkProtecting a Wireless Network

•• Wireless network range doesnWireless network range doesn’’t stop at thet stop at theproperty lineproperty line

•• Default device and network ID settingsDefault device and network ID settingsallow intruders to enter the networkallow intruders to enter the network

•• Internet bandwidth can be stolenInternet bandwidth can be stolen•• Computers can be vulnerable to hackerComputers can be vulnerable to hacker

intrusion and takeoverintrusion and takeover

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Computer Threats: VirusesComputer Threats: Viruses

•• A program that attaches itself to anotherA program that attaches itself to anotherprogram and spreads itself to otherprogram and spreads itself to othercomputerscomputers

•• Viruses are hidden within the code of aViruses are hidden within the code of ahost programhost program

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How Does a ComputerHow Does a ComputerCatch a Virus?Catch a Virus?

•• Viruses copyViruses copythemselvesthemselves

•• Infect a file onInfect a file onyour computeryour computer

•• Spread by sharingSpread by sharingdisks disks or flashdrives

•• E-mailE-mailattachments areattachments arethe most likelythe most likelysource of a virussource of a virus

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What Viruses DoWhat Viruses Do

•• Replicate themselves:Replicate themselves:–– Slow down networksSlow down networks

•• Secondary objectives:Secondary objectives:–– Display annoying messagesDisplay annoying messages–– Delete files on the hard driveDelete files on the hard drive–– Change computer settingsChange computer settings

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Types of VirusesTypes of Viruses•• Boot-sector virusesBoot-sector viruses

–– Replicate themselves in the boot sector of the hardReplicate themselves in the boot sector of the harddrivedrive

•• Logic bombsLogic bombs–– Activate when certain conditions are metActivate when certain conditions are met

•• Time bombsTime bombs–– Viruses that are triggered by the passage of time orViruses that are triggered by the passage of time or

on a certain dateon a certain date•• WormsWorms

–– Travel between systems through networksTravel between systems through networks

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Types of VirusesTypes of Viruses•• Script viruses:Script viruses:

–– Hidden on Web pages as mini programsHidden on Web pages as mini programs•• Macro viruses:Macro viruses:

–– Attached to documentsAttached to documents–– Series of commandsSeries of commands

•• E-mail virusE-mail virus–– Use e-mail address book to distribute the virusUse e-mail address book to distribute the virus

•• Encryption virusesEncryption viruses–– Compresses files using a complex encryption keyCompresses files using a complex encryption key–– User must pay to get the files unlockedUser must pay to get the files unlocked

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Virus ClassificationsVirus Classifications

• Polymorphic viruses:– Periodically rewrite themselves to avoid

detection• Multipartite viruses:

– Infect multiple file types• Stealth viruses:

– Erase their code from the hard drive andreside in the active memory

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Antivirus SoftwareAntivirus Software•• Programs designed to detect viruses:Programs designed to detect viruses:

–– Scan files looking for virus signatures (unique code)Scan files looking for virus signatures (unique code)–– Provide options for deleting or fixing infected filesProvide options for deleting or fixing infected files–– Inoculate files against further infectionInoculate files against further infection

•• Detect known virusesDetect known viruses•• Antivirus programs need to be updated frequentlyAntivirus programs need to be updated frequently