She married and later divorced Lazare Bloch. In 1925, she and Bloch (they remained business partners after the divorce) founded an economic newspaper, La Gazette du Franc et des Nations. Hanau used the newspaper to dispense stock tips to financial speculators.
Hanau's paper promoted mainly the stocks and securities of her own business partners, whose businesses were mere shells or paper companies. Still, the value of their stock kept rising when stockbrokers bought and traded them. Hanau expanded her investing advice network and later formed her own financial news agency, Agence Interpresse. She even released short-term bonds that promised 8% interest.
Now, French banks and Agence Havas, the rival financial news agency, turned against her. Banks began to investigate the nonexistent companies and soon, there were numerous rumors about Hanau's shady business practices. At first, Hanau managed to quell the rumors by bribing cooperative politicians.
However, when charges continued to swirl around her, police arrested Hanau, Bloch and many of their business partners on 17 December 1928. They were charged with fraud and confined in St. Lazare prison. By then, her investors had lost approximately 120,000,000 contemporary French francs.
The preliminary trial began 15 months later. Hanau protested that the court did not understand financial business, that she could return all the money and that she should be released on bail. When court denied the bail, she went on a hunger strike.
Three weeks later, Hanau was moved to the hôpital Cochin in Paris, where she was forcibly fed. When she was left alone, she made a rope out of bedsheets, climbed out of the window and returned to St. Lazare prison. Police chief Jean Chiappe, a Corsican, was afraid that she would die in his hands and requested for her to be released on bail. She was moved to a hospice, where she still announced that she would return all the money, but not everybody believed her.
Her trial began in earnest on 20 February 1932. During the trial, Hanau revealed the names of all the politicians that she had bribed and caused a scandal. Hanau received two years in prison, but the court credited her with the 15 months she had already spent in prison. Bloch received 18 months, and their other partners were released with fines.
When Hanau was released later that year, she bought the Forces magazine. In April 1932, she published an article about the shady side of the financial markets and quoted a Sûreté file about herself. Police arrested her but she refused to reveal who had leaked the file, just that it had been taken from the Financial Minister Flandin. She was sentenced to 3 months in prison for receiving classified information. She appealed, but when the appeal was rejected, she fled. She was soon arrested and returned to prison.
- "Justice Is Rotten", TIME Magazine, 4 June 1934 issue
- The TIME Magazine article indicates that the three-month sentenced was for contempt of court after had she declared that "Justice Is Rotten" and that she would loudly say so whenever she was brought before a court.
- Brakeman, Lynne (1997). Chronology of Women Worldwide: People, Places & Events that Shaped Women's History. Gale. p. 334. ISBN 978-0787601546.
- Janet Flanner, "The Swindling Presidente," The New Yorker, 26 August & 2 September 1939.