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Chapter 12 Designing System Interfaces, Controls, and Security

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Presentation on theme: "Chapter 12 Designing System Interfaces, Controls, and Security"— Presentation transcript:

1 Chapter 12 Designing System Interfaces, Controls, and Security
Systems Analysis and Design in a Changing World, 3rd Edition

2 Identifying System Interfaces
Systems interfaces are broadly defined as inputs or outputs with minimal or no human intervention Inputs from other systems (messages, EDI) Highly automated input devices such as scanners Inputs that are from data in external databases Outputs that are to external databases Outputs with minimal HCI Outputs to other systems Real-time connections (both input and output)

3 Full Range of Inputs and Outputs

4 eXtensible Markup Language (XML)
Extension of HTML that embeds self-defined data structures within textual messages Transaction that contains data fields can be sent with XML codes to define meaning of data fields XML provides common system-to-system interface XML is simple and readable by people Web services is based on XML to send business transactions over Internet

5 System-to-System Interface Based on XML

6 Design of System Inputs
Identify devices and mechanisms used to enter input High-level review of most up-to-date methods to enter data Identify all system inputs and develop list of data content with each Provides link between design of application software and design of user and system interfaces Determine controls and security necessary for each system input

7 Input Devices and Mechanisms
Capture data as close to origination source as possible Use electronic devices and automatic entry whenever possible Avoid human involvement as much as possible Seek information in electronic form to avoid data reentry Validate and correct information at entry point

8 Prevalent Input Devices to Avoid Human Data Entry
Magnetic card strip readers Bar-code readers Optical character recognition readers and scanners Touch screens and devices Electronic pens and writing surfaces Digitizers, such as digital cameras and digital audio devices

9 Defining the Details of System Inputs
Ensure all data inputs are identified and specified correctly Can use traditional structured models Identify automation boundary Use DFD fragments Segment by program boundaries Examine Structure Charts Analyze each module and data couple List individual data fields

10 Automation Boundary on a System-level DFD

11 Create New Order DFD with an Automation Boundary

12 List of Inputs for Customer Support System

13 Structure Chart for Create New Order

14 Data Flows, Data Couples, and Data Elements Making up Inputs

15 Using Object-Oriented Models
Identifying user and system inputs with OO approach has same tasks as traditional approach OO diagrams are used instead of DFDs and structure charts System sequence diagrams identify each incoming message Design class diagrams identify and describe input parameters and contain pseudocode to verify characteristics of inputs

16 Partial System Sequence Diagram for Payroll System Use Cases

17 System Sequence Diagram for Create New Order

18 Input Messages and Data Parameters from RMO System Sequence Diagram

19 Designing System Outputs
Determine each type of output Make list of specific system outputs required based on application design Specify any necessary controls to protect information provided in output Design and prototype output layout Ad hoc reports – designed as needed by user

20 Defining the Details of System Outputs
Type of reports Printed reports Electronic displays Turnaround documents May use traditional structured models to identify outputs Data flows crossing automation boundary Data couples and report data requirements on structure chart

21 Table of System Outputs Based on Traditional Structured Approach

22 Using Object-Oriented Models
Outputs indicated by messages in sequence diagrams Originate from internal system objects Sent to external actors or another external system Output messages based on an individual object are usually part of methods of that class object To report on all objects within a class, class-level method is used that works on entire class

23 Table of System Outputs Based on OO Messages

24 Designing Reports, Statements, and Turnaround Documents
Printed versus electronic Type of output reports Detailed Summary Exception Executive Internal versus external Graphical and multimedia presentation

25 RMO Summary Report with Drill Down to the Detailed Report

26 Sample Bar Chart and Pie Chart Reports

27 Formatting Reports What is objective of report?
Who is the intended audience? What is media for presentation? Avoid information overload Format considerations such as meaningful headings, date of information, date report produced, page numbers

28 Designing Integrity Controls
Mechanisms and procedures built into a system to safeguard it and information contained within Integrity controls Built into application and database system to safeguard information Security controls Built into operating system and network

29 Objectives of Integrity Controls
Ensure that only appropriate and correct business transactions occur Ensure that transactions are recorded and processed correctly Protect and safeguard assets of the organization Software Hardware Information

30 Points of Security and Integrity Controls

31 Input Integrity Controls
Used with all input mechanisms Additional level of verification to help reduce input errors Common control techniques Field combination controls Value limit controls Completeness controls Data validation controls

32 Database Integrity Controls
Access control Data encryption Transaction control Update control Backup and recovery protection

33 Output Integrity Controls
Ensures output arrives at proper destination and is correct, accurate, complete, and current Destination controls - output is channeled to correct people Completeness, accuracy, and correctness controls Appropriate information present on output

34 Integrity Controls to Prevent Fraud
Three conditions are present in fraud cases Personal pressure, such as desire to maintain extravagant lifestyle Rationalization, such as person’s thoughts that “I will repay this money” Opportunity, such as unverified cash receipts Control of fraud requires both manual procedures and computer integrity controls

35 Fraud Risks and Prevention Techniques

36 Designing Security Controls
Security controls protect assets of organization from all threats External threats such as hackers, viruses, worms, and message overload attacks Security control objectives Maintain stable, functioning operating environment for users and application systems (24 x 7) Protect information and transactions during transmission outside organization (public carriers)

37 Security for Access to Systems
Used to control access to any resource managed by operating system or network User categories Unauthorized user – no authorization to access Registered user – authorized to access system Privileged user – authorized to administrate system Organized so that all resources can be accessed with same unique ID/password combination

38 Users and Access Roles to Computer Systems

39 Managing User Access Most common technique is user ID / password
Authorization – Is user permitted to access? Access control list – users with rights to access Authentication – Is user who they claim to be? Smart card – computer readable plastic card with embedded security information Biometric devices – keystroke patterns, fingerprint, retinal scans, voice characteristics

40 Data Security Data and files themselves must be secure
Encryption – primary security method Altering data so unauthorized users cannot view Decryption Altering encrypted data back to original state Symmetric key – same key encrypts and decrypts Asymmetric key – different key decrypts Public key – public encrypts, private decrypts

41 Symmetric Key Encryption

42 Asymmetric Key Encryption

43 Digital signatures and certificates
Encryption of messages enables secure exchange of information between two entities with appropriate keys Digital signature encrypts document with private key to verify document author Digital certificate is institution’s name and public key that is encrypted and certified by third party Certifying authority Verisign or Equifax

44 Using a Digital Certificate

45 Secure Transactions Standard set of methods and protocols for authentication, authorization, privacy, integrity Secure Sockets Layer (SSL) renamed as Transport Layer Security (TLS) – protocol for secure channel to send messages over Internet IP Security (IPSec) – newer standard for secure Internet message transmission Secure Hypertext Transport Protocol (HTTPS or HTTP-S) – standard for transmitting Web pages securely (encryption, digital signing, certificates)

46 Summary System interfaces all inputs/outputs except (GUI)
Designing inputs to system is three-step process Identify devices/mechanisms used to enter input Identify system inputs, develop list of data content Determine controls and security necessary for each system input Traditional approach to design inputs and outputs DFDs, data flow definitions, structure charts

47 Summary (continued) OO approach to design inputs and outputs
Sequence diagrams, class diagrams, DFDs Integrity controls and security designed into system Only appropriate and correct business transactions occur Transactions are recorded and processed correctly Protect and safeguard assets of the organization Control access to resources

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