Shadow Broker
From Mass Effect Wiki
The Shadow Broker is a "necessary evil of galactic politics" who buys and sells information to the highest bidder. It isn't a direct threat to anyone, but is a resource people use. The Broker appears to be a genius at handling information - all the secrets that are bought and sold seem to even out, and no one ever gets the upper hand, meaning the Broker always stays in business. The Shadow Broker's identity and gender is unknown because the Broker always works through agents. Barla Von refers to the Broker as "he" for convenience's sake, but he tells Commander Shepard that he personally thinks the Shadow Broker is a whole group of individuals. Otherwise it doesn't seem possible to keep track of all that information and have such a wide sphere of influence.
The Shadow Broker was part of the reason Tali came to the Citadel: the data file she had proving Saren Arterius had gone rogue put her in danger, but was too valuable to waste. She wanted to trade the information for a safe place to hide, so Dr. Chloe Michel put her in touch with the club owner Fist, who worked for the Broker. However, unknown to her, Fist had changed his allegiances to Saren. The Broker was so angry at him that Wrex was hired to take Fist out.
After raiding the Cerberus base on Nepheron as part of UNC: Hades' Dogs, an agent for the Shadow Broker actually contacts Shepard aboard the Normandy, wanting to buy the Cerberus files the team managed to recover. Apparently Admiral Kahoku bought the Broker's services to track Cerberus down, in return for passing on any files he discovered. Shepard can agree to sell the information or refuse. Agreeing earns credits and Renegade points. If Shepard refuses, the Shadow Broker's agent claims the information will be dug out of the Alliance databases eventually anyway and you will receive Paragon points. Either way, the Shadow Broker's agent assures Shepard that this encounter will not be forgotten by his employer. It is believed the Shadow Broker will have a continued role in the Mass Effect trilogy, since he appears to wield a lot of power and influence within the Mass Effect universe.
