When fraud happens within an organization’s accounting system, there is often a paper (or digital) trail left behind. It’s unavoidable, as there is a record of something related to the fraud, whether it is a legitimate invoice that was later adjusted, an account balance that was changed, or a fake employee who was added to the payroll system.
Frauds involving bribery and corruption are different. They happen almost completely outside the accounting system, so they often don’t leave a paper trail. Management instead must rely on tips or other vague clues to the existence of such a fraud scheme.
Bribery and corruption typically arise out of relationships between people, so in order to detect them, management must often be aware of the personal relationships between employees and outside parties. That is clearly a difficult task, and often nearly impossible.