Chapter 15 Controlling ComputerBased Information Systems Part I

Chapter 15 Controlling Computer-Based Information Systems, Part I

Objectives for Chapter 15 • Features of a CBIS environment and the control objectives in SAS 78 • Threats to the operating system and controls used to minimize exposures • Techniques used to control access to the database • Incompatible functions in a CBIS environment • Controls necessary to regulate systems development and maintenance activities • Controls of an organization’s computer facilities and the disaster recovery options

Controls, CBIS & SAS 78 • Transaction authorization – may be embedded into the programs • Segregation of duties – Duties that must be separated in a manual system may be combined in a computerized setting. – The computer-based functions of programming, processing, and maintenance must be separated.

Segregation of Duties Control Objectives • Transaction authorization is separate from transaction processing. • Asset custody is separate from recordkeeping responsibilities. • The sub-tasks needed to process the transactions are separated so that no individual or group is responsible for transaction authorization, transaction recording, and asset custody.

Segregation of Duties Control Objective 1 Authorization Control Objective 2 Authorization Processing Custody Control Objective 3 Authorization Task 1 Task 2 TRANSACTION Recording Task 3 Task 4

Controls, CBIS & SAS 78 • Supervision - more supervision is typically necessary in a CBIS because: – highly skilled employees generally have a higher turnover rate – highly skilled employees are often in positions of authority – physical observation of employees working with the system is often difficult or impractical

Controls, CBIS & SAS 78 • Accounting records – Source documents and ledgers may be stored magnetically with no “paper trail. ” – Expertise is required to understand the links. • Access control – Tight control is necessary over access to programs and files. – Fraud is easier to commit since records are located in one data repository.

Controls, CBIS & SAS 78 • Independent verification – need to review the internal logic of programs and comparison of accounting records and physical assets – management must assess: § the performance of individuals § the integrity of the transaction processing system § the correctness of data contained in accounting records

General Control Framework for CBIS Exposures 10 control components need to be addressed: – operating system – data management – organizational structure – systems development – systems maintenance – computer center security – internet and Intranet – EDI – personal computer – applications

Organizational Structure Internet & Intranet Operating System Data Management Internet & Intranet Systems Development EDI Trading Partners Systems Maintenance Personal Computers Applications Computer Center Security General Control Framework for CBIS Exposures

Operating System Controls • The operating systems performs three main tasks: – translates high-level languages into the machine-level language – allocates computer resources to user applications – manages the tasks of job scheduling and multiprogramming.

For An Operating System To Perform These Tasks Consistently And Reliably, It Must… • protect itself from tampering from users • be able to prevent users from tampering with the programs of other users • be able to safeguard users’ applications from accidental corruption • be able to safeguard its own programs from accidental corruption • be able to protect itself from power failures or other disasters

Operating System Security • Log-On Procedure – first line of defense--user IDs and passwords • Access Token – contains key information about the user • Access Control List – defines access privileges of users • Discretionary Access Control – allows user to grant access to another user

Operating System Control Techniques • Access privilege controls – determine who can access what data in the system • Password controls – reusable passwords – one-time passwords • Malicious and destructive programs controls – protection against virus, worms, logic bombs, etc. • System audit trail controls – keystroke monitoring – event monitoring

Operating System Control Dangers • Browsing – looking through memory for sensitive information (e. g. , in the printer queue) • Masquerading – pretend to be an authorized user by getting id and passwords • Virus & Worms – foreign programs that spread through the system – virus must attach to another program, worms are self-contained

Operating System Control Dangers • Trojan Horse – foreign program that conceals itself with another legitimately imported program • Logic Bomb – foreign programs triggered by a specific event • Back Door – alternative entry into system

Anti-Virus Software ñcan prevent the initial infection by write protecting the file ñcan detect the infection of known viruses ñcan sometimes remove the infection ñmust stay current

Organizational Structure Internet & Intranet Operating System Data Management Internet & Intranet Systems Development EDI Trading Partners Systems Maintenance Personal Computers Applications Computer Center Security General Control Framework for CBIS Exposures

Data Management Controls Two crucial control issues: Access controls Backup controls

Access Controls • User views - based on sub-schemas • Database authorization table - allows greater authority to be specified • User-defined procedures - user to create a personal security program or routine • Data encryption - encoding algorithms • Biometric devices - fingerprints, retina prints, or signature characteristics • Inference controls - necessary in systems which allow queries

Subschema Restricting Access

Computer Resource Authority Table List Resource User Ticket User 1 User 2 User 3 AR File Read data Change Add Delete Read only No Access Employee Line Cash Receipts File Printer Program No Access Read only Use Use No Access Read code Modify Delete No Access

Data Management Controls • Backup options: – grandparent-child backup - the number of generations to backup is a policy issue – direct access file backup - back-up masterfile at pre-determined intervals – off-site storage - guard against disasters and/or physical destruction

Backup Controls • Database environment – database backup - automatic periodic backup – transaction log (journal) - a list of transactions which provides an audit trail of all processed transactions – checkpoint features - suspends all data processing while the system performs reconciliation – recovery module - restarts the system after a failure

Organizational Structure Internet & Intranet Operating System Data Management Internet & Intranet Systems Development EDI Trading Partners Systems Maintenance Personal Computers Applications Computer Center Security General Control Framework for CBIS Exposures

Organizational Structure Controls The two main CBIS environments have different exposures and IC requirements: Centralized DP Distributed DP

President CENTRALIZED COMPUTER SERVICES FUNCTION VP Marketing VP Computer Services Database Administration Systems Development New Systems Development Systems Maintenance DISTRIBUTED ORGANIZATIONAL STRUCTURE Data Control VP Finance Data Processing Data Preparation Computer Operations Data Library President VP Marketing VP Finance Treasurer IPU VP Operations VP Administration Manager Plant X Controller IPU IPU Manager Plant Y IPU

Centralized DP Organizational Controls • In centralized IS, need to separate: – systems development from computer operations – database administrator and other computer service functions • especially database administrator (authorizing) and systems development (processing) • DBA authorizes access – maintenance and new systems development – data library and operations

Distributed DP Organizational Controls • Distributed Data Processing: despite many advantages of this approach, control implications are present – incompatible software among the various work centers – data redundancy may result – consolidation of incompatible tasks – difficulty hiring qualified professionals – lack of standards

Organizational Structure Controls • A corporate computer services function/information center may help to alleviate the potential problems associated with DDP by providing: – central testing of commercial hardware and software – a user services staff – a standard-setting body – reviewing technical credentials of prospective systems professionals

Organizational Structure Internet & Intranet Operating System Data Management Internet & Intranet Systems Development EDI Trading Partners Systems Maintenance Personal Computers Applications Computer Center Security General Control Framework for CBIS Exposures

Systems Development Life Cycle Business Needs and Strategy Legacy Situation Business Requirements 1. Systems Strategy - Assessment - Develop Strategic Plan System Interfaces, Architecture and User Requirements Feedback: User requests for New Systems High Priority Proposals undergo Additional Study and Development 2. Project Initiation - Feasibility Study - Analysis - Conceptual Design - Cost/Benefit Analysis Selected System Proposals go forward for Detailed Design 3. In-house Development Feedback: User requests for System Improvements and Support 4. Commercial Packages - Construct - Deliver - Configure - Test - Roll-out New and Revised Systems Enter into Production 5. Maintenance & Support - User help desk - Configuration Management - Risk Management & Security

Systems Development Controls • New systems must be authorized. • User needs and requests should be formally documented. • Technical design activities should be documented. • Internal auditors should participate in the development process. • All program modules must be thoroughly tested before they are implemented. • Individual modules must be tested by a team of users, internal audit staff, and systems professionals.

Organizational Structure Internet & Intranet Operating System Data Management Internet & Intranet Systems Development EDI Trading Partners Systems Maintenance Applications Personal Computers Computer Center Security General Control Framework for CBIS Exposures

System Maintenance Controls • Last, longest and most costly phase of SDLC – 80 -90% of entire cost of a system • All maintenance actions should require – technical specifications – testing – documentation updates – formal authorizations for any changes made

SPL • Source program library (SPL) – library of applications and software – place where programs are developed and modified – once compiled into machine language, no longer vulnerable

Uncontrolled Access to the Source Program Library

A Controlled SPL Environment • An SPL Management System (SPLMS) can be used to protect the SPL environment by controlling the following functions: – storing programs on the SPL – retrieving programs for maintenance purposes – deleting obsolete programs from the library – documenting program changes to provide an audit trail of the changes

Source Program Library under the Control of SPL Management Software

SPL Control Features • Password control • Separation of test libraries • Reports that enhance management control and the audit function • Assigns program version numbers automatically • Controlled access to maintenance commands • Documentation and authorization of changes

Organizational Structure Internet & Intranet Operating System Data Management Internet & Intranet Systems Development EDI Trading Partners Systems Maintenance Personal Computers Applications Computer Center Security General Control Framework for CBIS Exposures

Computer Center Controls Considerations: • location away from human-made and natural hazards • utility and communications lines underground • windows closed and air filtration systems in place • access limited to the operators and other necessary workers; others required to sign in and out • fire suppressions systems should be installed • backup power supplies

Disaster Recovery Planning • Disaster recovery plan (DRP) – all actions to be taken before, during, and after a disaster – Disaster Recovery Team (DRT) identified – critical applications must be identified • restore these applications first • Backups & off-site storage procedures – databases and applications – documentation – supplies

Second-Site Disaster Backups • The Empty Shell - involves two or more user organizations that buy or lease a building and remodel it into a computer site, but without computer equipment • The Recovery Operations Center - a completely equipped site; very costly and typically shared among many companies • Internally Provided Backup - companies with multiple data processing centers may create internal excess capacity