What is the purpose of the internal audit function?

"Internal Audit teams exist to offer risk management to an organization by catching errors, flaws and fraud before an external audit is conducted. The Sarbanes-Oxley Act amplified the need for internal audit functions by requiring management of a company to certify in writing that the financial statements are accurately presented. Internal audit teams help give management confidence in the financials by evaluating the effectiveness of internal controls, corporate governance and accounting processes."