Auditing the Audit Trail Is Your System's Log Actually Useful?
Published on: Sat Aug 10 2024 by Ivar Strand
Auditing the Audit Trail: Is Your System’s Log Actually Useful?
The “audit trail” is a standard feature of virtually every modern financial software package. It is presented by vendors as a cornerstone of internal control and is often a key requirement in procurement processes. It is meant to provide an authoritative, chronological record of all activities within the system.
However, the mere existence of a log file is not a control in itself. In our forensic and assurance work, we frequently find that these vaunted audit trails lack the detail, integrity, and accessibility required for any meaningful investigation. The critical question for any fiduciary is not “Do you have an audit trail?” but “Is your audit trail forensically sound?”
The Difference Between a Log and an Audit Trail
It is essential to distinguish between a basic system log and a genuine audit trail. A simple log may only record high-level events, such as a user login or the creation of a new record.
A forensically sound audit trail is far more comprehensive. It is a secure, time-stamped, and immutable record of the full lifecycle of a transaction. It must contain sufficient detail to allow an independent party to reconstruct events, understand the changes that were made, and attribute every critical action to a specific individual.
Core Attributes of a Forensically Sound Audit Trail
To assess the quality of a system’s logs, we use a framework based on five core attributes. A log that fails to meet these criteria is of limited value for serious forensic or auditing work.
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Completeness (The “What”). A useful log must capture not only that a record was changed, but precisely what was changed. For every modification to a critical data field (e.g., a payment amount, a bank account number, an approval status), the log must record the “before” and “after” values.
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Attribution (The “Who”). Every entry in the log must be unambiguously tied to a unique user ID. Logs that attribute actions to generic system-level accounts are insufficient, as they obscure individual responsibility.
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Temporality (The “When”). Each action must be recorded with a secure, server-generated timestamp. This timestamp must be reliable and protected from user alteration. For programs operating across multiple countries, the log must also be clear about which timezone is being used.
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Immutability (The “Cannot Be Changed”). This is the most critical attribute. Can the logs be edited or deleted by any user, including a system administrator? If an administrator can alter the logs to conceal illicit activity, the audit trail has no integrity. A robust system must protect its logs from any modification.
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Accessibility (The “Can Be Used”). An audit trail is only useful if it can be accessed and analyzed. The logs should be available to auditors in a human-readable format (e.g., CSV or text file) that can be easily exported for analysis without requiring proprietary software or direct intervention from the vendor.
How to Test Your Audit Trail’s Integrity
You can perform a basic assessment of your audit trail without deep technical knowledge.
- The “Change and Check” Test: Make a specific, documented change to a test transaction—alter a payment amount by a small, unique figure. Then, ask your IT team or vendor to immediately provide you with the full audit log for that specific transaction. Check if it correctly captured the “who, what (before and after values), and when” of your change.
- The Administrator Question: Ask a direct question of your IT administrator or vendor: “What technical controls prevent you, as an administrator, from editing or deleting entries from this log?” The directness of the question can often reveal weaknesses in the system’s security design.
An audit trail is not merely a feature; it is a fundamental control. Verifying its integrity is a non-negotiable step in building a system that is not just trusted, but demonstrably trustworthy.
