"You can do all the fancy pictures you want, but if you have the name of 10 buyers that's way more important, " says Mr. Taylor, who adds that his firm's network of contacts helps him talk regularly to past clients about potential buyers.

WSJ: Brokers Who Bet on a Few Sales

This is software that sits at the edge of a firm's network and inspects the outgoing data traffic.

ECONOMIST: Companies and information

PC, which the unidentified worker then used to log on to the firm's corporate network.

ECONOMIST: Computer security: Worming out the truth | The