Signifyd today launches tools for online merchants to fight fraud. It helps sellers make better choices about whether to accept or deny sales by piecing together online identities that match up with offline people. Signifyd CEO Rajesh Ramanand, who formerly led risk-management divisions at FedEx and PayPal, calls this “context detection,” but really what he means is online sleuthing of buyers’ social graph, location, history and other factors to establish probable hypotheses (or a lack of them) for why someone might have made a fishy-looking transaction. For instance, Ramanand showed how someone buying a one-way plane ticket (red flag!) for a passenger with a different name (red flag!) coming from another country (red flag!) could actually be a valid transaction, because a bit of LinkedIn and Facebook friend-list stalking establishes that the buyer lives in the arrival city, and shows the ticket is for a visit from his sister-in-law.