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Networking and Security

Networking and Security. Connecting Computers and Protecting Them from Intruders. Networking Advantages and Disadvantages. Advantages Increased productivity More communication options Enable the sharing of resources Facilitate Internet connectivity Disadvantages Complexity Cost

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Networking and Security

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  1. Networking and Security Connecting Computers and Protecting Them from Intruders

  2. Networking Advantages and Disadvantages • Advantages • Increased productivity • More communication options • Enable the sharing of resources • Facilitate Internet connectivity • Disadvantages • Complexity • Cost • Materials • Personnel

  3. What is a Network? • Computer network: • Two or more computers connected together • Nodes: Any device connected to a network

  4. Network Architecture • Network designs: • Locally controlled: • Peer-to-peer (P2P) • Centrally controlled: • Client/server Peer-to-peer Client/server

  5. Peer-to-Peer Networks • Nodes communicate with each other: • Peers • Share peripheral devices: • Printers • Home and small office networks

  6. Client/Server Networks • Client computers: • Users • Server computers: • Provide resources to clients • Central control unit • Data flows efficiently • Servers respond to requests from clients • Scalable network

  7. Servers • Depending on the network size and work load servers can perform a single or multiple roles

  8. Dedicated Server Types • Application • Authentication • File • Database • Email • Web • Print

  9. Classifications of Client/Server Networks • LAN: local area network • Computers linked together over a small geographic region • WAN: wide area network • Computers linked together over large diverse geographic locations • MAN: metropolitan area network • Computers linked together within a city or county • PAN: personal area network • Wireless devices connected in close proximity to each other

  10. Network Topology • Physical layout of networks components • Bus • Ring • Star

  11. Bus Topology • All nodes are connected in sequence on a single cable • Used most often on peer-to-peer networks • Networked computers communicate with each other • One computer transmits data at a time: • Access methods avoid data collisions • Data is transmitted in “packets”

  12. Ring Topology • Nodes are laid out in a ring • Token (data packet) flows in one direction from device to device

  13. Star Topology • Nodes connect to a central communications device (hub/switch) • A node sends a signal to the hub which retransmits it to the other nodes • A node accepts the signal addressed to it

  14. Network Operating Systems (NOS) • Provide the protocol that controls the communication between devices on the network • Major network operating systems: • Windows Server 2003 • UNIX • Novell NetWare

  15. NIC Network Adapters • Devices connected to or installed in nodes: • Network interface cards (NIC) • External network adapter • Enable communication between nodes External adapter

  16. Wireless Adapters • Uses radio waves to connect nodes (2.4GHz) • Each node requires a wireless network adapter

  17. Transmission Media • Provides communications channel between nodes • Forms of media: • Telephone wire: • Twisted pair • Coaxial cable • Fiber-optic cable • Radio waves: • Wireless • Bandwidth: • Data transfer rate • Throughput • Measured in megabits per second (Mbps)

  18. Choosing a Cable • Maximum run length • Bandwidth • Bend radius • Cable cost • Installation costs • Susceptibility to interference • Signal transmission methods

  19. Twisted Pair Cable • Copper wire twisted around each other to reduce interference • STP- Shielded • UTP- Unshielded • Cat 5 • Cat 6

  20. Coaxial Cable • Four components: • Copper core • Nonconductive insulating material • Braided metal • Plastic cover

  21. Fiber-Optic Cable • Components include: • Glass or plastic fibers • Cladding • Outer jacket • Uses light impulses to transmit data • Immune to interference

  22. Network Navigation Devices • Devices that help make data flow possible • Repeaters • Hubs • Switches • Routers

  23. Ethernet Repeater and Hubs • Repeaters • Amplifies the signal • Hubs • Amplifies the signal • Simultaneous broadcasting • Acts like a cable splitter

  24. Ethernet Switches and Routers • Switches • Send data to specific nodes on the network • Routers • Communicates data between different networks

  25. Data Transmission and Protocols • Computer protocols are rules for electronic information exchange • Open system protocols: • Any computer can communicate with other computers using the same protocols • Circuit switching • Packet switching

  26. Circuit Switching • Dedicated connection between two points • Remains active until the transmission is terminated • Telephone communications

  27. Packet Switching • Data is broken into small units called packets • Packets are sent over various routes to their destination • Packets are reassembled by the receiving computer • Packets contain: • Destination/source addresses • Reassembling instructions • Data

  28. Ports • Source Ports - is assigned to the client and is used to keep track of user sessions. • Destination Ports - are used to route packets to the appropriate application. • Listening Ports - software that responds to a port number is said to be "listening" for its packets. • 65,535 ports • Well known ports are 0-1023. • Port 80 HTTP

  29. Headers • Encapsulation- layering of instructions onto the data • Headers are like mailing addresses and handling instructions • Contains information for the handling of the data block

  30. TCP, IP, UDP • TCP- Transmission Control Protocol • Reliable • Will resend lost packets • Error checking • Send in an orderly fashion • UDP - User Datagram Protocol • Faster • Less reliable • Streaming • Internet Protocol - specifies the format of packets

  31. MAC Address • Media Access Control address: hardware address that uniquely identifies each node of a network. • Example: 07-a1-34-ff-b5-df

  32. IP Addresses • Unique number that identifies NOS/devices connected to the Internet • Example: 134.68.76.100 • Static address: • Address never changes: Enter it manually • Dynamic address: • Temporary address: Automatically assigned

  33. Anatomy of a Data Packet

  34. OSI (Open Systems Interconnection) Model

  35. Questions?

  36. Network Security • Why attack a network rather than the computers on the network? • Lower risk of getting caught • Less work • Availability of tools • Numerous methods

  37. Networking Attack Methods • Sniffing • Spoofing • DoS – Denial of Service • Port Scanning

  38. Ethereal- Packet Sniffer

  39. Netstumbler - Wireless Network Scanner

  40. NetScan- Port Scanner

  41. Wireless Security or Lack Thereof • Lack of user awareness • No authentication • Pervasiveness • Tools are easily available • Poor security design • Weak encryption • Enabled defaults • Admin PW • Broncast on • SSID

  42. 150ft = 6 Houses, 1 street

  43. 450ft = 40 houses, 4 streets

  44. WWWD 2004 Stats • 228537 APs found • 140890 No WEP (60+%) • Wired Equivalent Privacy • 71850 Default SSID (30+%) • Service Set IDentifier • 62859 Default SSID and No WEP (27+%)

  45. Wireless Math Open wireless + Netstumbler = War Driving + GPS + Internet = http://www.wifimaps.com/

  46. Wireless Security Best Practices • Change default settings • Admin password • SSID – Service Set identifier • Rename • Choose wisely • Turn on WEP encryption • Disable SSID Broadcast • Create a VPN and use encryption

  47. Wireless Security Paradoxs and Myths • MAC filtering • Disable SSID Broadcast • Disable DHCP • Antenna placement • WEP Enabled

  48. Network Security • Firewalls: Block unused ports • Protects against port scanning • Authentication: • User ID and password used to access the network • Access privileges: • Close access to unused network systems • Use encryption and VPNs • Monitor your network • Fake APs • Watch traffic • Scan detectors

  49. Links http://netstats.indiana.edu/wanmap/index.html http://reviews.cnet.com/Bandwidth_meter/7004-7254_7-0.html

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