Title: Controlling Computer-Based Information Systems, Part I
1Chapter 15
- Controlling Computer-Based Information
Systems, Part I
2Objectives 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 organizations computer facilities
and the disaster recovery options
3Controls, 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.
4Segregation of Duties Control Objectives
- Transaction authorization is separate from
transaction processing. - Asset custody is separate from record-keeping
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.
5Segregation of Duties
Processing
Control Objective 1
Custody
Recording
Control Objective 2
Custody
Recording
Control Objective 3
Task 3
Task 4
TRANSACTION
6Controls, 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
7Controls, 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.
8Controls, 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
9General 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
10Organizational Structure
Internet Intranet
Data Management
Operating System
Systems Development
Personal Computers
Systems Maintenance
EDI Trading Partners
Applications
Computer Center Security
General Control Framework for CBIS Exposures
11Organizational Structure
Internet Intranet
Data Management
Operating System
Systems Development
Personal Computers
Systems Maintenance
EDI Trading Partners
Applications
Computer Center Security
General Control Framework for CBIS Exposures
12Operating 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.
13For 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
14Operating 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
15Operating 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
16Operating 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
17Operating 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
18Anti-Virus Software
- can prevent the initial infection
by write protecting the file - can detect the infection of known viruses
- can sometimes remove the infection
- must stay current
19Organizational Structure
Internet Intranet
Data Management
Operating System
Systems Development
Personal Computers
Systems Maintenance
EDI Trading Partners
Applications
Computer Center Security
General Control Framework for CBIS Exposures
20Data Management Controls
-
- Two crucial control issues
-
Access controls Backup controls
21Access 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
22Subschema Restricting Access
23Computer Resource Authority Table
List
Resource
Employee Line Cash Receipts AR File
File Printer Program
User
Read data Change Add Delete
User 1
Ticket
No Access Use No Access
Read code No Access Use Modify Delete
Read only
User 2
No Access Read only Use No Access
User 3
24Data Management Controls
- Backup options
- grandparent-parent-child backup - the number of
generations to backup is a policy issue - direct access file backup - back-up master-file
at pre-determined intervals - off-site storage - guard against
disasters and/or physical destruction
25Backup 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
26Organizational Structure
Internet Intranet
Data Management
Operating System
Systems Development
Personal Computers
Systems Maintenance
EDI Trading Partners
Applications
Computer Center Security
General Control Framework for CBIS Exposures
27Organizational Structure Controls
- The two main CBIS environments have different
exposures and IC requirements -
- Centralized DP Distributed DP
28President
CENTRALIZED COMPUTER SERVICES FUNCTION
VP Marketing
VP Computer Services
VP Operations
VP Finance
Database Administration
Data Processing
Systems Development
New Systems Development
Data Control
Data Preparation
Data Library
Systems Maintenance
Computer Operations
DISTRIBUTED ORGANIZATIONAL STRUCTURE
President
VP Marketing
VP Finance
VP Operations
VP Administration
Manager Plant X
Manager Plant Y
Treasurer
Controller
IPU
IPU
IPU
IPU
IPU
IPU
29Centralized 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
30Distributed 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
31Organizational 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
32Organizational Structure
Internet Intranet
Data Management
Operating System
Systems Development
Personal Computers
Systems Maintenance
EDI Trading Partners
Applications
Computer Center Security
General Control Framework for CBIS Exposures
33Systems Development Life Cycle
Business Needs and Strategy
Legacy Situation
Business Requirements
1. Systems Strategy - Assessment - Develop
Strategic Plan
FeedbackUser requests for New Systems
System Interfaces, Architecture and User
Requirements
High Priority Proposals undergo Additional Study
and Development
2. Project Initiation - Feasibility Study -
Analysis - Conceptual Design -
Cost/Benefit Analysis
FeedbackUser requests for System Improvements
and Support
Selected System Proposals go forward for Detailed
Design
3. In-house Development - Construct -
Deliver
4. Commercial Packages - Configure - Test -
Roll-out
New and Revised Systems Enter into Production
5. Maintenance Support - User help desk -
Configuration Management - Risk Management
Security
34Systems 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.
35Organizational Structure
Internet Intranet
Data Management
Operating System
Systems Development
Personal Computers
Systems Maintenance
EDI Trading Partners
Applications
Computer Center Security
General Control Framework for CBIS Exposures
36System 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
37SPL
- Source program library (SPL)
- library of applications and software
- place where programs are developed and modified
- once compiled into machine language, no longer
vulnerable
38Uncontrolled Access to the Source Program Library
39A 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
40Source Program Library under the Control of SPL
Management Software
41SPL 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
42Organizational Structure
Internet Intranet
Data Management
Operating System
Systems Development
Personal Computers
Systems Maintenance
EDI Trading Partners
Applications
Computer Center Security
General Control Framework for CBIS Exposures
43Computer 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
44Disaster 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
45Second-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