Derivatives, once labeled as 'Weapon of Mass Destructions' by Warren Buffet - The Oracle of Omaha, helped his investment firms - Berkshire Hathaway post a net income of $3.06 billion for the September- December quarter, from $117 million for the same period a year ago.

The Nebraska-based company said in its annual report that net income for the year 2009 stood at $8.06 billion, a 61 per cent gain from the year before, but considerably down from $13.2 billion it earned in 2007. Revenue for 2009 was at $112 billion in 2009, up from $108 billion in 2008.

Derivatives contributed $1.05 billion to the fourth quarter earnings, as compared to a loss of $4.61 billion a year earlier.

The annual report revealed Berkshire owned 1.9 per cent, of Sanofi as of December 2009, up from 1.7 per cent, a year earlier. Berkshire also increased its stake in Tesco - the British retail chain, to 234.2 million shares, or 3 per cent. The Conglomerate holding firm also revealed 9.9 per cent stake in BYD Company - a Chinese car and battery maker, the value of which has been swelled to more than eight times what Berkshire paid initially.