Rogue trading is all in a day's work, says Nick Leeson who toppled Barings Bank in 1995 with illicit trading worth $1.6 billion, but the $7.2 billion fraud that cost France's banking giant Societe Generale is frightening.

"Rogue trading is probably a daily occurrence within the financial markets," Leeson told the BBC. "What shocked me was the size. I never for one moment believed it would get to this degree of magnitude, this degree of loss."

Societe Generale's losses are four times greater than that caused by Leeson who spent six-and-a-half years in jail for the caper in Singapore.

The Financial Times said the rogue trader is Jerome Kerviel, 31, a mid-level employee who earned $145,000 a year in the bank's Delta One products team in Paris. Societe Generale did not confirm nor deny the report.

"I'm convinced he acted alone," said Jean-Pierre Mustier, chief executive of the corporate and investment banking division after interviewing the trader soon after the fraud was uncovered, BBC reported.

"The transactions which involved the fraud were simple - taking a position on shares rising - but hidden using extremely sophisticated and varied techniques," chief executive Daniel Bouton said in a letter to the bank's customers.