I just finished "The Blue Nowhere" by Jeffrey Deaver. He's the same author who wrote the book, "The Bone Collector, and some other good ones.
It's about a computer hacker who creates a program to go into anyone's computer, get information on them, and then he "social engineers" them to make them think he's someone they know or trust, then he kills them. It's pretty interesting, all the stuff they do to try to catch this guy. (It's all fiction, of course.)