HAPTER 10 Information Systems Controls for System Reliability Part 3: Processing Integrity and Availability
INTRODUCTION • Questions to be addressed in this chapter include: • What controls ensure processing integrity? • What controls ensure that the system is available when needed?
PROCESSING INTEGRITY • A reliable system produces information that is accurate, timely, reflects results of only authorized transactions, and includes outcomes of all activities engaged in by the organization during a given period of time. • Requires controls over both data input quality and the processing of the data. SYSTEMS RELIABILITY CONFIDENTIALITY PROCESSING INTEGRITY PRIVACY AVAILABILITY SECURITY
Controls Ensuring Processing Integrity • Input • Process • Output
Input Controls • Forms Design • Pre-numbered forms/ sequence test • Turnaround documents • Authorization and segregation of duties • Cancellation and storage of documents • Visual scanning
Input Controls • Data Entry Controls (Edit checks) • Field check • Sign check • Limit check • Range check • Size (or capacity) check • Completeness check • Validity check • Reasonableness test • Check digit verification • Key verification
Input Controls • The preceding tests are used for batch processing and online real-time processing. • Both processing approaches also have some additional controls that are unique to each approach.
Batch Input Controls • Batch Processing • Input multiple source documents at once in a group • In addition to the preceding controls, when using batch processing, the following data entry controls should be incorporated. • Sequence check • Error log • Batch totals
Batch Input Controls • Batch Totals • Compare input totals to output totals • Financial • Sums a field that contains monetary values • Hash • Sums a nonfinancial numeric field • Record count • The number of records in a batch
Online Data Entry Controls • Additional online data entry controls • Online processing data entry controls include: • Automatic entry of data • Prompting • Closed-loop verification • Transaction logs • Error messages
Processing Controls • Processing controls to ensure that data is processed correctly include: • Data matching • File labels • Recalculation of batch totals • Cross-footing balance test • Write-protection mechanisms • Concurrent update controls
Output Controls • Careful checking of system output provides additional control over processing integrity. • Output controls include: • User review of output • Reconciliation procedures • External data reconciliation • Data transmission controls
Output Controls • Data Transmission Controls • Two basic types of data transmission controls: • Checksums – hash of file transmitted, comparison made of hash before and after transmission • Parity checking
Output Controls • Parity checking • Computers represent characters as a set of binary digits (bits). • For example, “5” is represented by the seven-bit pattern 0000101. • When data are transmitted some bits may be lost or received incorrectly. • Two basic schemes to detect these events are referred to as even parity and odd parity. • In either case, an additional bit is added to the digit being transmitted.
AVAILABILITY • Reliable systems are available for use whenever needed. • Threats to system availability originate from many sources, including: • Hardware and software failures • Natural and man-made disasters • Human error • Worms and viruses • Denial-of-service attacks and other sabotage SYSTEMS RELIABILITY CONFIDENTIALITY PROCESSING INTEGRITY PRIVACY AVAILABILITY SECURITY
Controls Ensuring Availability • Systems or information need to be available 24/7 • It is not possible to ensure this so:
AVAILABILITY • Minimizing Risk of System Downtime • Loss of system availability can cause significant financial losses, especially if the system affected is essential to e-commerce. • Organizations can take a variety of steps to minimize the risk of system downtime.
AVAILABILITY • Preventive maintenance can reduce risk of hardware and software failure. Examples: • Cleaning disk drivers • Properly storing magnetic and optical media • Use of redundant components can provide fault tolerance, which enables the system to continue functioning despite failure of a component. Examples: • Dual processors • Arrays of multiple hard drives.
AVAILABILITY • Risks associated with natural and man-made disasters can be reduced with proper location and design of rooms housing mission-critical servers and databases. • Raised floors protect from flood damage. • Fire protection and suppression devices reduce likelihood of fire damage. • Adequate air conditioning reduces likelihood of damage from over-heating or humidity. • Cables with special plugs that cannot be easily removed reduce risk of damage due to accidentally unplugging.
AVAILABILITY • Surge protection devices provide protection against temporary power fluctuations. • An uninterruptible power supply (UPS) provides protection from a prolonged power outage and buys the system enough time to back up critical data and shut down safely.
AVAILABILITY • Training • Well-trained operators are less likely to make mistakes and more able to recover if they do. • Security awareness training, particularly concerning safe email and web-browsing practices, can reduce risk of virus and worm infection. • Patch management and antivirus software • Anti-virus software should be installed, run, and kept current. • Email should be scanned for viruses at both the server and desktop levels. • Newly acquired software and disks, CDs, or DVDs should be scanned and tested first on a machine that is isolated from the main network.
AVAILABILITY • Recovery and Resumption of Normal Operations • Data backup procedures • Disaster recovery plan (DRP) • Business continuity plan (BCP)
AVAILABILITY • Data Backup Procedures • Data need to be backed up regularly and frequently. • A backup is an exact copy of the most current version of a database, file, or software program. It is intended for use in the event of a hardware or software failure. • The process of installing the backup copy for use is called restoration.
AVAILABILITY • A full backup is an exact copy of the data recorded on another physical media (tape, magnetic disk, CD, DVD, etc.) • Full backups are time consuming, so most organizations: • Do full backups weekly • Supplement with daily partial backups. • incremental backup- copy only data that changed since the last partial backup • differential backup – copy only data that changed from last full back-up
AVAILABILITY • Whichever backup procedure is used, multiple backup copies should be created: • One can be stored on-site for use in minor incidents. • At least one additional copy should be stored off-site to be safe should a disaster occur
AVAILABILITY • Disaster Recovery and Business Continuity PlanningObjectives: • Minimize the extent of the disruption, damage, and loss • Temporarily establish an alternative means of processing information • Resume normal operations as soon as possible • Train and familiarize personnel with emergency operations • Recovery point objective (RPO) • Recovery time objective (RTO)
AVAILABILITY • Infrastructure Replacement • Major disasters can totally destroy an organization’s information processing center or make it inaccessible. • A key component of disaster recovery and business continuity plans incorporates provisions for replacing the necessary computing infrastructure, including: • Computers • Network equipment and access • Telephone lines • Office equipment • Supplies • It may even be necessary to hire temporary staff.
AVAILABILITY • Organizations have three basic options for replacing computer and networking equipment. • Reciprocal agreements • Cold sites • Hot sites
AVAILABILITY • Documentation • An important and often overlooked component. Should include: • The disaster recovery plan itself, including instructions for notifying appropriate staff and the steps to resume operation, needs to be well documented. • Assignment of responsibility for the various activities. • Vendor documentation of hardware and software. • Documentation of modifications made to the default configuration (so replacement will have the same functionality). • Detailed operating instructions. • Copies of all documentation should be stored both on-site and off-site.
AVAILABILITY • Testing • Periodic testing and revision is probably the most important component of effective disaster recovery and business continuity plans. • Most plans fail their initial test, because it’s impossible to anticipate everything that could go wrong. • The time to discover these problems is before the actual emergency and in a setting where the weaknesses can be carefully analyzed and appropriate changes made.
AVAILABILITY • Insurance • Organizations should acquire adequate insurance coverage to defray part or all of the expenses associated with implementing their disaster recovery and business continuity plans.