ais6e-140607034514-phpapp01.ppt

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

Comparing HTML and XML

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.

File Server

LAN

LAN

Node

Node

Node

Node

Printer Server

Files

Printer

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).

LANLAN

Bridge

GatewayGateway

LAN

WAN

WAN

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.

Server

Ring Topology

Local Files

Local Files

Local Files

Local Files

Local Files

CentralFiles

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

Advantages of EDI

Reduction or elimination of data entryReduction of errorsReduction of paperReduction of paper processing and

postageReduction of inventories (via JIT

systems)