© 2008 Prentice-Hall, Inc. 1 Technology in Action Chapter 8 Behind the Scenes: Networking and Security

© 2008 Prentice-Hall, Inc. 2 Chapter Topics Advantages of business networks Client/server vs. peer-to-peer networks Classifications of client/server networks Client/server network components Types of transmission media Network adapters Moving data in a client/server network Securing networks

© 2008 Prentice-Hall, Inc. 3 Networking Advantages Networks Increase productivity Enable the sharing of hardware resources Enable the sharing of software Facilitate communication inside and outside the company

© 2008 Prentice-Hall, Inc. 4 Network Advantages Sharing networked hardware can reduce costs Sharing networked hardware can provide access to a wide range of services and specialized peripheral devices Sharing networked software can reduce costs Sharing data on a network is easy Networks enable people to work together regardless of time and place (telecommuting)

© 2008 Prentice-Hall, Inc. 5 Network Challenges Networks may be vulnerable to unauthorized access from many sources and locations More vulnerable than standalone computers Wireless networks can be tapped from a “snooping” computer Networked computers are susceptible to an increasing number of worms, Trojan horses, and blended threats

© 2008 Prentice-Hall, Inc. 6 Organizational Structure: Client/Server and Peer-to-Peer Where are the resources? Centralized – Client/Server resources in the Server(s) Distributed – Peer-to-Peer (file sharing) resources in all the machines

© 2008 Prentice-Hall, Inc. 7 Organizational Structure: Client/Server and Peer-to-Peer

© 2008 Prentice-Hall, Inc. 8 Client/Server Networks Server-based network Clients and servers Data flows efficiently Servers respond to requests from clients Servers perform specific tasks Scalable network Centralized

© 2008 Prentice-Hall, Inc. 9 Classifications of Client/Server Networks LAN Local area network Computers linked together over a small geographic region

© 2008 Prentice-Hall, Inc. 10 Classifications of Client/Server Networks WAN Wide area network Computers linked over large geographic locations MAN Metropolitan area network Computers linked together within a city or county

© 2008 Prentice-Hall, Inc. 11 Classifications of Client/Server Networks PAN Personal area network Wireless devices connected in close proximity to each other Intranet Private corporate network using TCP/IP Protected by a firewall from the Internet outside

© 2008 Prentice-Hall, Inc. 12 Constructing Client/Server Networks Servers Transmission media Network adapters Network navigation devices

© 2008 Prentice-Hall, Inc. 13 Servers Number and type of servers depend on network size and workload Dedicated server Performs one specific function Authentication server Keeps track of network logins and services available File server Stores and manages files

© 2008 Prentice-Hall, Inc. 14 Dedicated Servers Communications server Handles communications between networks including the Internet Often the only device on the network directly connected to the Internet Web server Hosts a Web site available through the Internet

© 2008 Prentice-Hall, Inc. 15 Dedicated Servers, cont'd Print server Manages client-requested printing jobs Creates print queue (prioritizes print jobs) Applications server Acts as a storage area for application software Database server Provides clients with access to database information server Processes and delivers incoming and outgoing

© 2008 Prentice-Hall, Inc. 16 Transmission Media The routes data takes to flow between devices on a network Wired Wireless

© 2008 Prentice-Hall, Inc. 17 Network Links Wired network Twisted-pair cable Coaxial cable Fiber-optic cable Wireless network RF signals Microwaves Infrared light

© 2008 Prentice-Hall, Inc. 18

© 2008 Prentice-Hall, Inc. 19 Choosing a Cable Maximum run length Bandwidth Bend radius Cable cost Installation costs Susceptibility to interference Comparison of Characteristics of Major Cable Types Cable Characteristics Twisted Pair (Cat 6)Coaxial (ThinNet)Coaxial (ThickNet)Fiber-Optic Maximum Run Length 328 feet (100 m)607 feet (185 m)1,640 feet (500m)Up to 62 miles (100 km) Bandwidth 1,000 Mbps10 Mbps 100 Mbps to 2 Gbps Bend Radius (Flexibility) No limit360 degrees/foot30 degrees/foot Cable Cost Very lowLowModerateHigh Installation Cost Very lowLowSlightly higher than ThinNet Most expensive because of Installation training required Susceptibility to Interference HighLowVery lowNone (not susceptible to EMI and RFI)

© 2008 Prentice-Hall, Inc. 20 Twisted Pair Cable Pairs of copper wire twisted around each other Twists make the wires less susceptible to interference Shielded twisted pair (STP) Layer of foil shielding Unshielded twisted pair (UTP) Cat 5E: Bandwidth 200 Mbps Cat 6: Bandwidth 1 Gbps No foil layer UTP STP

© 2008 Prentice-Hall, Inc. 21 Coaxial Cable Four components Copper core Nonconductive insulating material Braided metal Plastic cover

© 2008 Prentice-Hall, Inc. 22 Fiber-Optic Cable Components include Glass or plastic fibers Cladding Outer jacket Uses light impulses to transmit data Immune to interference Physically smaller More difficult to install

© 2008 Prentice-Hall, Inc. 23 Network Adapters Devices that enable computers to communicate on a network Network interface cards (NICs) Three functions Generate network transmission signals Create data packets Act as information gatekeepers Ethernet compliant Wireless NICs

© 2008 Prentice-Hall, Inc. Wired Ethernet Networks Protocol created by Xerox PARC in 70’s Bandwidth from 10/100 Mbps to 1 Gbps Connection with Unshielded Twisted Pair Cat 5, Cat 5E, Cat 6 Network interface card added if not builtin Switch device works to send data where it goes, avoiding collisions Routers work between two networks, like your network and the Internet 24

© 2008 Prentice-Hall, Inc. Wireless Ethernet Networks Use radio instead of wires Wi-Fi = standard Need a wireless network adapter for each machine – transmits and receives signals Radio signals can be blocked by walls, reduced by distance WAP – wireless access point – will extend the range 25

© 2008 Prentice-Hall, Inc. 26 Wireless Media Standard Wi-Fi, short for Wireless Fidelity b – first cost-effective wireless devices a, g – bandwidth increased to 54 Mbps Super G – bandwidth to 108 Mbps n – will support higher throughput and greatly increased range

© 2008 Prentice-Hall, Inc. Grid computing Loosely connected networks of machines volunteered to work on research Donate your unused cycles to research CPUs are idle a lot, software has been written to make use of those idle machine cycles Download software that connects you SETI, medicine, mathematics, astrophysics Make sure it’s a project that is legitimate 27

© 2008 Prentice-Hall, Inc. “Cloud computing” The Internet is “the cloud” Your data is stored on servers remotely, not on your local hard drive Applications you run (even Office) are via a web browser Portable Cheaper? “software as service” Like plugging into the wall vs. owning a generator 28

© 2008 Prentice-Hall, Inc. 29 Network Security Threats Human Errors and Mistakes Accidents and mistakes Malicious Human Activity Current and former employees hacking or planting viruses Natural Events and Disasters Hurricanes, floods, fire

© 2008 Prentice-Hall, Inc. 30 Computer Threats Hackers and Crackers Viruses Trojan Horses Worms Bots Combating Malicious Code "Malware"

© 2008 Prentice-Hall, Inc. 31 Hackers and Crackers Why do they do it? To show off their technical expertise blackmail espionage industrial military Theft Global terrorism

© 2008 Prentice-Hall, Inc. 32 Viruses Viruses are malicious code that enters a computer and disrupts normal operation Viruses might deliver a payload, which could either be annoying or devastating Trigger events can unleash some viruses When you check On a certain date/time When your computer starts up

© 2008 Prentice-Hall, Inc. 33 Viruses Computer viruses attach themselves to a file, reproduce, and spread to other files and computers File virus Boot sector virus Macro / script virus virus Main goal is to reproduce itself Attempts to be unnoticed - stealth mode Depends on the user to execute a program or open a file to get started

© 2008 Prentice-Hall, Inc. 34 Trojan Horses Seems to perform one function while doing another Keyloggers record your keystrokes Backdoors allow unauthorized access to computers Wants to be noticed - looks desirable to get itself installed A funny video or a cool game

© 2008 Prentice-Hall, Inc. 35 Worms Designed to spread from computer to computer - more active than a virus or Trojan Will send ITSELF without user knowledge if there is a network connection available Mass-mailing worms spread to addresses in the address book on the infected computer Examples include Klez, Netsky, Sasser Messages sometimes contain a spoofed address

© 2008 Prentice-Hall, Inc. 36 Bots A bot is software that can automate a task or autonomously execute a task Bots can be useful – system administrators use them to do repetitive work more quickly than a human could, “spiders” are bots Bots can be the payload of a virus or Trojan Botnets are linked bot-infested computers Bots can be networked to make a botnet Used for “DOS” attacks

© 2008 Prentice-Hall, Inc. 37 What can they do? Malicious code can perform the following activities: Network traffic jam Denial of Service attacks Bot nets Browser reconfiguration Delete and modify files Access confidential information Performance degradation Disable antivirus and firewall software

© 2008 Prentice-Hall, Inc. 38 Network Security Authentication User ID and password used to access the network Use of a possessed object for access Access privileges Enable access to certain network systems Physical protection measures Restrict physical access to sensitive network equipment Magnetic card readers Biometric access devices

© 2008 Prentice-Hall, Inc. 39 Network Security Firewalls Prevent access to the network by unauthorized users Composed of software and/or hardware Screen and validate data packets Software firewalls Norton, McAfee, ZoneAlarm, BlackICE Hardware firewalls Usually built into routers

© 2008 Prentice-Hall, Inc. 40 Network Firewall Layout

© 2008 Prentice-Hall, Inc. 41 Combating Malicious Code Use antivirus software and firewall software on every computing device you own keep them up to date Virus signatures keep changing McAfee software freely available on download.uky.edu to all UK students AVG software free for home usewww.avg.com Do not open suspicious attachments Regularly download and install the latest security patches available for your OS, program, and browser.

© 2008 Prentice-Hall, Inc. 42 Combating Malicious Code Limit sharing disks and other removable storage media. Only download programs from reputable Web sites. Limit the amount of file-sharing you do Use anti-virus software to scan all s and all files received from someone else Backup your files regularly Look for unexpected file extensions – like exe on a jpg file Test your computer with Gibson Research’s free scan

© 2008 Prentice-Hall, Inc. Protecting a Wireless Network Change your network’s name Disable the broadcast of its name (SSID) Change the default password on your router Turn on WEP (wired equivalent privacy) (weak) or WPA (wi-fi protected access) Turn on MAC addresses – so only computers whose addresses you enter are allowed on Keep software up to date 43