In modern systems, audit trails are usually stored online as text files that can be read
by word processing and spreadsheet programs. Data extraction CAATTs such as ACL
are capable of searching log files for specific records to verify completeness and accuracy
of the output reports. Alternatively, the auditor can test output controls directly using
ITF. A well-designed ITF system will permit the auditor to produce a batch of sample
transactions, including some error records, and trace them through all phases of processing,
error detection, and output reporting.