The US bank is believed to have invested $450m in Facebook, while DST has provided a further $50m.
Facebook, which has more than 550 million users worldwide, refused to comment on the deal this morning. It was valued at $10bn in May 2009, after DST paid $200m for a 2% equity stake in the company.
The valuation has triggered speculation that Facebook could be considering an initial public offering.
Facebook's chief executive Mark Zuckerberg, who co-founded the site in 2004, was named Time Magazine's Person of the Year in 2010. He is estimated to have a fortune of $14bn.