When it comes to fighting fraud, financial statement audits have much less impact than other methods. A survey of workplace fraud conducted by the Association of Certified Fraud Examiners (ACFE) shows that hotlines do the most to cut companies' losses from fraud, and surprise audits and fraud training are also more effective than internal or external audits.

For example, companies that use hotlines had median fraud losses of $100,000, or 59% lower than the median loss of $245,000 for companies without hotlines. Surprise audits cut companies' median loss by 51.5%, from a median of $244,000 to $100,000, and fraud training for employers cut losses by 50%, from $200,000 to $100,000. Internal audits cut fraud by just 30.6%, according to the ACFE survey, while external audits of financial statements cut fraud just 25%.

"The controls that rated the highest in terms of reducing your loss to fraud were not the things we think of traditionally as fraud detection controls," says John Warren, ACFE's general counsel. "External audits, internal audits, management review–those all ranked in the bottom half of the control list. The things that ranked high, other than hotlines, were things like antifraud training, codes of conduct and employee support programs.