Information Systems Audit: The Basics

In the early days of computers, many people were suspicious of their ability to replace human beings performing complex tasks. The first business software applications were mostly in the domain of finance and accounting. The numbers from paper statements and receipts were entered into the computer, which would perform calculations and create reports. Computers were audited using sampling techniques. An auditor would collect the original paper statements and receipts, manually perform the calculations used to create each report, and compare the results of the manual calculation with those generated by the computer. In the early days, accountants would often find programming errors, and these were computer audit findings.

However, these exercises also sometimes yielded findings of fraud. Fraud activities ranged from data entry clerks changing check payees to programmers making deliberate rounding errors designed to accumulate cash balances in hidden bank accounts. [Editor's note: For more, see Essential Reading on Fraud.] As auditors recognized repeating patterns of fraud, they recommended a variety of security features designed to automatically prevent, detect, or recover from theft of assets.

As computers became more sophisticated, auditors recognized that they had fewer and fewer findings related to the correctness of calculations and more and more on the side of unauthorized access. Moreover, the checks and balances that were devised to maintain correctness of calculations were implemented as software change control measures. These rely heavily on security to enforce controls over segregation of duties between programming, testing, and deployment staff. This meant that even programming changes relied in some measure for their effectiveness on computer security controls. Nowadays, information systems audit seems almost synonymous with information security control testing.

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