Technology In Action
Networking and Security
Connecting Computers and Protecting Them
from Intruders
© 2006 Prentice-Hall, Inc.
1
Technology In Action
Networking Advantages and
Disadvantages
• Advantages
–
–
–
–
Increased productivity
More communication options
Enable the sharing of resources
Facilitate Internet connectivity
• Disadvantages
– Complexity
– Cost
 Materials
 Personnel
© 2006 Prentice-Hall, Inc.
2
Technology In Action
What is a Network?
• Computer network:
– Two or more computers connected together
– Nodes: Any device connected to a network
© 2006 Prentice-Hall, Inc.
3
Technology In Action
Network Architecture
• Network designs:
– Locally controlled:
 Peer-to-peer (P2P)
– Centrally controlled:
 Client/server
Peer-to-peer
Client/
server
© 2006 Prentice-Hall, Inc.
4
Technology In Action
Peer-to-Peer Networks
• Nodes communicate
with each other:
– Peers
• Share peripheral
devices:
– Printers
• Home and small office
networks
© 2006 Prentice-Hall, Inc.
5
Technology In Action
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
© 2006 Prentice-Hall, Inc.
6
Technology In Action
Servers
• Depending on the
network size and work
load servers can
perform a single or
multiple roles
© 2006 Prentice-Hall, Inc.
7
Technology In Action
Dedicated Server Types
•
•
•
•
•
•
•
© 2006 Prentice-Hall, Inc.
Application
Authentication
File
Database
Email
Web
Print
8
Technology In Action
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
© 2006 Prentice-Hall, Inc.
9
Technology In Action
Network Topology
• Physical layout of
networks
components
– Bus
– Ring
– Star
© 2006 Prentice-Hall, Inc.
10
Technology In Action
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”
© 2006 Prentice-Hall, Inc.
11
Technology In Action
Ring Topology
• Nodes are laid out in
a ring
• Token (data packet)
flows in one direction
from device to device
© 2006 Prentice-Hall, Inc.
12
Technology In Action
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
© 2006 Prentice-Hall, Inc.
13
Technology In Action
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
© 2006 Prentice-Hall, Inc.
14
Technology In Action
Network Adapters
• Devices connected to or installed in nodes:
– Network interface cards (NIC)
– External network adapter
• Enable communication between nodes
NIC
© 2006 Prentice-Hall, Inc.
External
adapter
15
Technology In Action
Wireless Adapters
• Uses radio waves to connect nodes
(2.4GHz)
• Each node requires a wireless network
adapter
© 2006 Prentice-Hall, Inc.
16
Technology In Action
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)
© 2006 Prentice-Hall, Inc.
17
Technology In Action
Choosing a Cable
•
•
•
•
•
•
•
Maximum run length
Bandwidth
Bend radius
Cable cost
Installation costs
Susceptibility to interference
Signal transmission methods
© 2006 Prentice-Hall, Inc.
18
Technology In Action
Twisted Pair Cable
• Copper wire twisted
around each other to
reduce interference
• STP- Shielded
• UTP- Unshielded
– Cat 5
– Cat 6
© 2006 Prentice-Hall, Inc.
19
Technology In Action
Coaxial Cable
• Four components:
–
–
–
–
Copper core
Nonconductive insulating material
Braided metal
Plastic cover
© 2006 Prentice-Hall, Inc.
20
Technology In Action
Fiber-Optic Cable
• Components include:
– Glass or plastic fibers
– Cladding
– Outer jacket
• Uses light impulses to transmit data
• Immune to interference
© 2006 Prentice-Hall, Inc.
21
Technology In Action
Network Navigation Devices
• Devices that help make
data flow possible
– Repeaters
– Hubs
– Switches
– Routers
© 2006 Prentice-Hall, Inc.
22
Technology In Action
Ethernet Repeater and Hubs
• Repeaters
– Amplifies the signal
• Hubs
– Amplifies the signal
– Simultaneous
broadcasting
– Acts like a cable
splitter
© 2006 Prentice-Hall, Inc.
23
Technology In Action
Ethernet Switches and Routers
• Switches
– Send data to specific
nodes on the network
• Routers
– Communicates data
between different
networks
© 2006 Prentice-Hall, Inc.
24
Technology In Action
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
© 2006 Prentice-Hall, Inc.
25
Technology In Action
Circuit Switching
• Dedicated connection between two points
• Remains active until the transmission is
terminated
• Telephone communications
© 2006 Prentice-Hall, Inc.
26
Technology In Action
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
© 2006 Prentice-Hall, Inc.
27
Technology In Action
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
© 2006 Prentice-Hall, Inc.
28
Technology In Action
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
© 2006 Prentice-Hall, Inc.
29
Technology In Action
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
© 2006 Prentice-Hall, Inc.
30
Technology In Action
MAC Address
• Media Access Control address: hardware
address that uniquely identifies each node
of a network.
• Example: 07-a1-34-ff-b5-df
© 2006 Prentice-Hall, Inc.
31
Technology In Action
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
© 2006 Prentice-Hall, Inc.
32
Technology In Action
Anatomy of a Data Packet
© 2006 Prentice-Hall, Inc.
33
Technology In Action
OSI (Open Systems Interconnection) Model
© 2006 Prentice-Hall, Inc.
34
Technology In Action
© 2006 Prentice-Hall, Inc.
35
Technology In Action
Questions?
© 2006 Prentice-Hall, Inc.
36
Technology In Action
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
© 2006 Prentice-Hall, Inc.
37
Technology In Action
Networking Attack Methods
•
•
•
•
Sniffing
Spoofing
DoS – Denial of Service
Port Scanning
© 2006 Prentice-Hall, Inc.
38
Technology In Action
Ethereal- Packet Sniffer
© 2006 Prentice-Hall, Inc.
39
Technology In Action
Netstumbler - Wireless Network
Scanner
© 2006 Prentice-Hall, Inc.
40
Technology In Action
NetScan- Port Scanner
© 2006 Prentice-Hall, Inc.
41
Technology In Action
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
© 2006 Prentice-Hall, Inc.
42
Technology In Action
150ft = 6 Houses, 1 street
© 2006 Prentice-Hall, Inc.
43
Technology In Action
450ft = 40 houses, 4 streets
© 2006 Prentice-Hall, Inc.
44
Technology In Action
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+%)
© 2006 Prentice-Hall, Inc.
45
Technology In Action
Wireless Math
Open wireless + Netstumbler =
War Driving + GPS + Internet =
http://www.wifimaps.com/
© 2006 Prentice-Hall, Inc.
46
Technology In Action
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
© 2006 Prentice-Hall, Inc.
47
Technology In Action
Wireless Security Paradoxs and
Myths
•
•
•
•
•
MAC filtering
Disable SSID Broadcast
Disable DHCP
Antenna placement
WEP Enabled
© 2006 Prentice-Hall, Inc.
48
Technology In Action
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
© 2006 Prentice-Hall, Inc.
49
Technology In Action
Links
http://netstats.indiana.edu/wanmap/index.h
tml
http://reviews.cnet.com/Bandwidth_meter/
7004-7254_7-0.html
© 2006 Prentice-Hall, Inc.
50