This type of fraud could be perpetrated with little assistance. He didn't keep the records of all the individual accounts, but only of the total invested. From that original false balance sheet, done by Madoff alone, with no assistance from anybody else working for him, everything else could then be generated. Employees were not likely to realize they were helping to perpetrate a fraud. Frauds over $1 billion are easier to perpetrate than frauds of $10,000 to $10,000,000. That's because for very large dollar amounts, what auditors rely upon is not independent third party documents of original entry, but the word of the CEO and CFO. Bernard Madoff's word was gold: his brokerage firm had been a reputable market maker for decades. When he entered another line of business, being an investment manager with discretion, his reputation followed him. Somewhere along the line, he gave into temptation and just kept on giving and giving into it.