The Neighbor - Lisa Gardner [112]
“Take the rule of five-twelve. That’s the magic number in forensic computer analysis. See, inside a hard drive are round platters that spin around to read and write data. These platters contain chunks of five hundred and twelve bytes of data, and they’re constantly whirling under the seeker head. The seeker head, then, must divide all information into five hundred and twelve byte chunks in order to store the data onto the platters.”
“Okay.” D.D. went to work slicing up her pancetta.
“Now, say you’re saving a file to your hard drive that doesn’t divide neatly into five hundred and twelve byte chunks. It’s not one thousand and twenty-four bytes of data, it’s eight hundred bytes. The computer will fill one whole data chunk, then half of another available chunk. Then what? The computer doesn’t pick up where it left off, mid-data chunk. Instead, a new file will start with a fresh five-twelve byte space, meaning the previous file has excess storage capacity, or what we call ‘slack space,’ in the existing data chunk. Often, old data gets left in that slack space. Say you called up that file, made some changes, then resaved it. The overwrite might not go exactly on top of the old data the way most people assume. Instead it might be tucked somewhere else inside the same data chunk. Then a guy like me can search that five-twelve chunk. In the slack space I might find the old document where you wrote the original letter asking your lover to murder your spouse, as well as the revised doc, where you deleted that particular paragraph. And voila, one guilty conviction is born.”
“I don’t have a spouse,” D.D. volunteered, having another bite of eggs, “though I’m now deeply suspicious of my computer.”
Wayne Reynolds grinned at her. “You probably should be. People have no idea how much information is retained unknowingly on their hard drives. I like to say a computer is like a guilty conscience. It remembers everything and you never know when it might start to speak.”
“You been teaching your skills to Ethan?” D.D. asked.
“Haven’t had to. Kid absorbs it on his own. If I can corral his skills for good versus evil, he’ll be a hell of an investigator one day.”
“What constitutes the dark side for computer technology?”
Wayne shrugged. “Hacking, code breaking, illicit data-mining. Ethan is a good kid, but he’s also thirteen, so following in his uncle’s footsteps doesn’t sound as exciting as it once did. Join the state police or join the Internet underground. You be the judge.”
“He seems to have valued Sandy Jones’s opinions.” D.D. had finished her food; she pushed back the white ceramic plate.
Wayne was thoughtful for a moment. “Ethan believes he is in love with his teacher,” he conceded at last.
“Did he have sex with her?”
“I doubt it.”
“Why?”
“She didn’t view him that way.”
“And how would you know?”
“Because I was seeing Sandra myself, every Thursday night. At the basketball games.”
“Ethan contacted me regarding Sandra,” Wayne explained a few moments later. They had paid the bill, left the coffee shop. Walking and talking seemed a better idea, given the subject matter. They headed aimlessly toward the waterfront, following the red line mapping the route once ridden by Paul Revere.
“My understanding,” Wayne continued now, “was that Sandra had approached Ethan about developing a teaching module for the Internet. It didn’t take Ethan long, however, to determine that her interest in online security ran deeper than mere classroom application. He believed her husband was up to something, perhaps involving child porn, and that Sandra was desperate to get to the bottom of it.”
“You didn’t open a case file?”
Wayne shook his head. “Couldn’t. First time I met with Sandra, she made it clear that she would only accept my involvement as a personal favor. Until she learned exactly what was going on, she didn’t want the police involved. She had to think