SocGen said that a 31-year-old trader named Jérôme Kerviel took massive "directional positions"—transactions that depend on the ability to correctly predict how the price of a security will move over time—that ended up costing the bank about 5 billion Euros.

Kerviel, who was previously an IT employee at SocGen before being moved to the front office, made over 1000 fraudulent transactions dating back to Sept. 2004 (with, the report says, a massive uptick in March 2007). He concealed the frauds using various techniques that exploited his in-depth knowledge of the bank's computer systems systems and procedures. His techniques allowed him to bypass with relative ease all the IT and process controls the bank had put in place to detect fraudulent transactions.

The bank's General Inspection Department last week released a 71-page report (download PDF) on the incident, following a 27-page preliminary report released in February (download PDF). The report, called Mission Green, highlighted five reasons the bank failed to detect Kerviel's activities despite several signs that in retrospect should have been obvious.

Supervision was lacking. Despite several internal alerts that should have triggered a closer look at his activities, Kerviel remained largely unsupervised, especially in the early part of 2007 when the bulk of his illegal activity took place. Between Sept. 2004 and Jan. 2007, his direct managers completely failed to detect any fraudulent activity, though there were several internal alerts. Kerviel's direct manager resigned in January 2007, and he did not have another until April; during this two and a half month period Kerviel was largely unsupervised and himself validated the earnings of his operational center.

A new desk manager assigned to Kerviel in April 2007 was ineffective and weak and did not have enough support from his superiors. Kerviel's direct manager had no specific knowledge of trading practices, and no attempts were made to verify his supervisory abilities. During the second half of last year the desk manager and his immediate superior were caught up with other projects and in dealing with high employee turnover rates; thus distracted, they missed Kerviel's activities. The manager did not carry out an analysis of the earnings generated by his traders—a task that was supposed to be one of his primary responsibilities.