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Accounting Information Systems, 6th edition
James A. Hall
COPYRIGHT © 2009 South-Western, a division of Cengage Learning. Cengage Learning and South-Western
are trademarks used herein under license
Objectives for Chapter 12Topologies that are employed to achieve connectivity across
the InternetProtocols and understand the specific purposes served by
several Internet protocolsBusiness benefits associated with Internet commerce and be
aware of several Internet business modelsRisks associated with intranet and Internet electronic
commerceIssues of security, assurance, and trust pertaining to
electronic commerceElectronic commerce implications for the accounting
profession
What is E-Commerce? The electronic processing and transmission
of business dataelectronic buying and selling of goods and
serviceson-line delivery of digital productselectronic funds transfer (EFT)electronic trading of stocksdirect consumer marketing electronic data interchange (EDI) the Internet revolution
Internet TechnologiesPacket switching
messages are divided into small packetseach packet of the message takes a different routes
Virtual private network (VPN)a private network within a public network
Extranetsa password controlled network for private users
World Wide Web an Internet facility that links users locally and
globallyInternet addresses
e-mail addressURL addressIP address
Protocol Functions…facilitate the physical connection between
the network devicessynchronize the transfer of data between
physical devicesprovide a basis for error checking and
measuring network performancepromote compatibility among network
devicespromote network designs that are flexible,
expandable, and cost-effective
Internet ProtocolsTransfer Control Protocol/Internet Protocol
(TCP/IP) - controls how individual packets of data are formatted, transmitted, and received
Hypertext Transfer Protocol (HTTP) - controls web browsers
File Transfer Protocol (FTP) - used to transfer files across the internet
Simple Network Mail Protocol (SNMP) - e-mail
Secure Sockets Layer (SSL) and Secure Electronic Transmission (SET) - encryption schemes
Open System Interface (OSI)The International Standards
Organization developed a layered set of protocols called OSI.
The purpose of OSI is to provide standards by which the products of different manufacturers can interface with one another in a seamless interconnection at the user level.
The OSI Protocol
Layer 1 Physical
Layer 2 Data Link
Layer 3 Network
Layer 4 Transport
Layer 5 Session
Layer 6 Presentation
Layer 7 Application
SOFTWARE
HARDWARE Layer 1 Physical
Layer 2 Data Link
Layer 3 Network
Layer 4 Transport
Layer 5 Session
Layer 6 Presentation
Layer 7 Application
SOFTWARE
HARDWARE
DataManipulationTasks
DataCommunicationsTasks
Communications Channel
NODE 1 NODE 2
HARD
WARE
HARD
WARE
HTML: Hyper Text Markup LanguageFormat used to produce Web pages
defines the page layout, fonts, and graphic elements
used to lay out information for display in an appealing manner like one sees in magazines and newspapers
using both text and graphics (including pictures) appeals to users
Hypertext links to other documents on the WebEven more pertinent is HTML’s support for
hypertext links in text and graphics that enable the reader to ‘jump’ to another document located anywhere on the World Wide Web.
XML: eXtensible Markup Language
XML is a meta-language for describing markup languages.
Extensible means that any markup language can be created using XML. includes the creation of markup languages
capable of storing data in relational form, where tags (formatting commands) are mapped to data values
can be used to model the data structure of an organization’s internal database
XBRL: eXtensible Business Reporting LanguageXBRL is an XML-based language for standardizing
methods for preparing, publishing, and exchanging financial information, e.g., financial statements.
XBRL taxonomies are classification schemes. Advantages:
Business offer expanded financial information to all interested parties virtually instantaneously.
Companies that use XBRL database technology can further speed the process of reporting.
Consumers import XBRL documents into internal databases and analysis tools to greatly facilitate their decision-making processes.
Benefits of E-CommerceAccess to a worldwide customer and/or
supplier baseReductions in inventory investment and
carrying costsRapid creation of business partnerships to
fill emerging market niches Reductions in retail prices through lower
marketing costsReductions in procurement costsBetter customer service
The Internet Business ModelInformation level
using the Internet to display and make accessible information about the company, its products, services, and business policies
Transaction levelusing the Internet to accept orders from
customers and/or to place them with their suppliers
Distribution levelusing the Internet to sell and deliver digital
products to customers
Dynamic Virtual OrganizationPerhaps the greatest potential benefit to be derived from e-commerce is the firm’s ability to forge dynamic business alliances with other organizations to fill unique market niches as the opportunities arise.
Areas of General ConcernData Security: are stored and transmitted
data adequately protected?Business Policies: are policies publicly
stated and consistently followed?Privacy: how confidential are customer
and trading partner data?Business Process Integrity: how
accurately, completely, and consistently does the company processes its transactions?
Intranet RisksIntercepting network messages
sniffing: interception of user IDs, passwords, confidential e-mails, and financial data files
Accessing corporate databasesconnections to central databases increase the
risk that data will be accessible by employeesPrivileged employees
override privileges may allow unauthorized access to mission-critical data
Reluctance to prosecutefear of negative publicity leads to such
reluctance but encourages criminal behavior
Internet Risks to ConsumersHow serious is the risk?
National Consumer League: Internet fraud rose by 600% between 1997 and 1998
SEC: e-mail complaints alleging fraud rose from 12 per day in 1997 to 200-300 per day in 1999
Major areas of concern:Theft of credit card numbersTheft of passwordsConsumer privacy--cookies
Internet Risks to BusinessesIP spoofing: masquerading to gain access to a
Web server and/or to perpetrate an unlawful act without revealing one’s identity
Denial of service (DOS) attacks: assaulting a Web server to prevent it from servicing users particularly devastating to business entities that
cannot receive and process business transactionsOther malicious programs: viruses, worms,
logic bombs, and Trojan horses pose a threat to both Internet and Intranet users
SYN Flood DOS Attack
Sender Receiver
Step 1: SYN messages
Step 2: SYN/ACK
Step 3: ACK packet code
In a DOS Attack, the sender sends hundreds of messages, receives the SYN/ACK packet, but does not response with an ACK packet. This leaves thereceiver with clogged transmission ports, and legitimate messages cannot be received.
Three Common Types of DOS Attacks
SYN Flood – when the three-way handshake needed to establish an Internet connection occurs, the final acknowledgement is not sent by the DOS attacker, thereby tying-up the receiving server while it waits
Smurf – the DOS attacker uses numerous intermediary computer to flood the target computer with test messages, “pings”
Distributed DOS (DDOS) – can take the form of Smurf or SYN attacks, but distinguished by the vast number of “zombie” computers hi-jacked to launch the attacks
E-Commerce Security: Data Encryption
Encryption - A computer program transforms a clear message into a coded (ciphertext) form using an algorithm.
EncryptionProgram
EncryptionProgram
Ciphertext
Ciphertext
CommunicationSystem
CommunicationSystem
Key
Key
CleartextMessage
CleartextMessage
Public Key is used for encoding messages.
Message A Message B Message C Message D
Ciphertext Ciphertext Ciphertext Ciphertext
Multiple peoplemay have the public key (e.g., subordinates).
Private Key is used fordecoding messages.
Typically one person ora small number of peoplehave the private key (e.g., a supervisor).
Message A Message DMessage CMessage B
E-Commerce Security: Digital Authentication
Digital signature: electronic authentication technique that ensures that the transmitted message originated with the authorized sender and that it was not tampered with after the signature was applied
Digital certificate: like an electronic identification card that is used in conjunction with a public key encryption system to verify the authenticity of the message sender
E-Commerce Security: FirewallsFirewalls: software and hardware that
provide security by channeling all network connections through a control gateway
Network level firewallslow cost/low security access control uses a screening router to its destinationdoes not explicitly authenticate outside users penetrate the system using an IP spoofing
techniqueApplication level firewalls
high level/high cost customizable network security allows routine services and e-mail to pass through performs sophisticated functions such as logging or
user authentication for specific tasks
Local Area Networks (LAN)A federation of computers located close
together (on the same floor or in the same building) linked together to share data and hardware
The physical connection of workstations to the LAN is achieved through a network interface card (NIC) which fits into a PC’s expansion slot and contains the circuitry necessary for inter-node communications.
A server is used to store the network operating system, application programs, and data to be shared.
Wide Are Network (WAN)A WAN is a network that is dispersed
over a wider geographic area than a LAN. It typically requires the use of:gateways to connect different types of
LANsbridges to connect same-type LANs
WANs may use common carrier facilities, such as telephone lines, or they may use a Value Added Network (VAN).
Star TopologyA network of IPUs with a large
central computer (the host)The host computer has direct
connections to smaller computers, typically desktop or laptop PCs.
This topology is popular for mainframe computing.
All communications must go through the host computer, except for local computing.
Local Data Local Data
Local Data
Local Data
Central Data
POS
POS
POS
POSPOS
Topeka St. Louis
KansasCity
DallasTulsa
Star Network
Hierarchical TopologyA host computer is connected to several
levels of subordinate smaller computers in a master-slave relationship.
ProductionPlanning System
ProductionSchedulingSystem
RegionalSales System
WarehouseSystem
WarehouseSystem
ProductionSystem
ProductionSystem
SalesProcessingSystem
SalesProcessingSystem
SalesProcessingSystem
CorporateLevel
RegionalLevel
LocalLevel
Ring TopologyThis configuration eliminates the central
site. All nodes in this configuration are of equal status (peers).
Responsibility for managing communications is distributed among the nodes.
Common resources that are shared by all nodes can be centralized and managed by a file server that is also a node.
Bus TopologyThe nodes are all connected to a
common cable - the bus.Communications and file transfers
between workstations are controlled by a server.
It is generally less costly to install than a ring topology.
Server
Bus Topology
Node
Node
Node
Node
Local Files
Local FilesLocal Files
Local Files
Local FilesNode
Central Files
Print Server
Client-Server TopologyThis configuration distributes the
processing between the user’s (client’s) computer and the central file server.
Both types of computers are part of the network, but each is assigned functions that it best performs.
This approach reduces data communications traffic, thus reducing queues and increasing response time.
Server
Client-Server Topology
Client
Client
Client
Client
RecordSearchingCapabilities
Data ManipulationCapabilities
ClientData ManipulationCapabilities
Data ManipulationCapabilities
Data ManipulationCapabilities
Data ManipulationCapabilities
Common Files
Network Control Objectivesestablish a communications session between the sender and the receiver
manage the flow of data across the network
detect errors in data caused by line failure or signal degeneration
detect and resolve data collisions between competing nodes
POLLING METHOD OF CONTROLLING DATA COLLISIONS
MASTERLocked Locked
Locked
Polling Signal
Data Transmission
One Site, the “master,” polls the other “slave” sites to determine if they have data to transmit.If a slave responds in the affirmative, the master site locks the network while the data are transmitted.
Allows priorities to be set for data communications across the network
SLAVE
SLAVE
SLAVE
SLAVE
WAN
Server
Token Ring
Node
Node
Node
Central Files
Local Files
Local Files
Local Files
Contains data
Empty token
Carrier SensingA random access technique that detects collisions
when they occurThis technique is widely used--found on Ethernets.The node wishing to transmit listens to the line to
determine if in use. If it is, it waits a pre-specified time to transmit.
Collisions occur when nodes listen, hear no transmissions, and then simultaneously transmit. Data collides and the nodes are instructed to hang up and try again.
Disadvantage: The line may not be used optimally when multiple nodes are trying to transmit simultaneously.
What is Electronic Data Interchange (EDI)?
The exchange of business transaction information:between companiesin a standard format (ANSI X.12 or
EDIFACT)via a computerized information system
In “pure” EDI systems, human involvements is not necessary to approve transactions.
Communications LinksCompanies may have internal EDI
translation/communication software and hardware.
ORThey may subscribe to VANs to
perform this function without having to invest in personnel, software, and hardware.
EDI System
PurchasesSystem
EDI TranslationSoftware
EDI TranslationSoftware
CommunicationsSoftware
CommunicationsSoftware
OtherMailbox
OtherMailbox
CompanyA’s mailbox
CompanyB’s mailbox
Sales OrderSystem
ApplicationSoftware
ApplicationSoftware
Direct Connection
VAN
Company A Company B
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