-- The Seattle Times
"Stoll's is the ever-appealing story of the little man bucking the system...great fun to read...lively and thoroughly absorbing."
-- The Philadelphia Inquirer
"The Cuckoo's Egg is 'reader friendly,' even for those who have only the vaguest familiarity with computers...a true spy thriller....The hunt is gripping."
-- Chicago Tribune
"As exciting as any action novel....A gripping spy thriller."
-- The New York Times Book Review
Über den Autor und weitere Mitwirkende
An astronomer by training and a computer expert by accident, Cliff Stoll has become a leading authority on computer security, an issue recognized everywhere as among the most important security problems of our times. He has given talks for the FBI, CIA, and NSA, and has appeared before the U.S. Senate. Stoll is an astronomer at the Harvard-Smithsonian Center for Astrophysics and lives in Cambridge, Massachusetts.
Leseprobe. Abdruck erfolgt mit freundlicher Genehmigung der Rechteinhaber. Alle Rechte vorbehalten.
Me, a wizard? Until a week ago, I was an astronomer, contentedly designing telescope optics. Looking back on it, I'd lived in an academic dreamland. All these years, never planning for the future, right up to the day my grant money ran out.
Lucky for me that my laboratory recycled used astronomers. Instead of standing in the unemployment line, I found myself transferred from the Keck Observatory at the Lawrence Berkeley Lab, down to the computer center in the basement of the same building.
Well, hell, I could fake enough computing to impress astronomers, and maybe pick it up fast enough that my co-workers wouldn't catch on. Still, a computer wizard? Not me -- I'm an astronomer.
Now what? As I apathetically stared at my computer terminal, I still thought of planetary orbits and astrophysics. As new kid on the block, I had my choice of a cubicle with a window facing the Golden Gate Bridge, or an unventilated office with a wall of bookshelves. Swallowing my claustrophobia, I picked the office, hoping that nobody would notice when I slept under the desk. On either side were offices of two systems people, Wayne Graves and Dave Cleveland, the old hands of the system. I soon got to know my neighbors through their bickering.
Viewing everyone as incompetent or lazy, Wayne was crossthreaded with the rest of the staff. Yet he knew the system thoroughly, from the disk driver software up to the microwave antennas. Wayne was weaned on Digital Equipment Corporation's Vax computers and would tolerate nothing less: not IBM, not Unix, not Macintoshes.
Dave Cleveland, our serene Unix buddha, patiently listened to Wayne's running stream of computer comparisons. A rare meeting didn't have Wayne's pitch, "Vaxes are the choice of scientists everywhere and help build strong programs twelve ways." Dave retorted, "Look, you keep your Vax addicts happy and I'll handle the rest of the world." Dave never gave him the satisfaction of getting riled, and Wayne's complaints eventually trailed off to a mutter.
Great. First day on the job, sandwiched between two characters who were already ruining my daydreams with their periodic disputes.
At least nobody could complain about my appearance. I wore the standard Berkeley corporate uniform: grubby shirt, faded jeans, long hair, and cheap sneakers. Managers occasionally wore ties, but productivity went down on the days they did.
Together, Wayne, Dave, and I were to run the computers as a lab-wide utility. We managed a dozen mainframe computers -- giant workhorses for solving physics problems, together worth around six million dollars. The scientists using the computers were supposed to see a simple, powerful computing system, as reliable as the electric company. This meant keeping the machines running full time, around the clock. And just like the electric company, we charged for every cycle of computing that was used.
Of four thousand laboratory employees, perhaps a quarter used the main computers. Each of these one thousand accounts was tallied daily, and ledgers kept inside the computer. With an hour of computing costing three hundred dollars, our bookkeeping had to be accurate, so we kept track of every page printed, every block of disk space, and every minute of processor time. A separate computer gathered these statistics and sent monthly bills to laboratory departments.
And so it happened that on my second day at work, Dave wandered into my office, mumbling about a hiccup in the Unix accounting system. Someone must have used a few seconds of computing time without paying for it. The computer's books didn't quite balance; last month's bills of $2,387 showed a 75-cent shortfall.
Now, an error of a few thousand dollars is obvious and isn't hard to find. But errors in the pennies column arise from deeply buried problems, so finding these bugs is a natural test for a budding software wizard. Dave said that I ought to think about it.
"First-degree robbery, huh?" I responded.
"Figure it out, Cliff, and you'll amaze everyone," Dave said.
Well, this seemed like a fun toy, so I dug into the accounting program. I discovered our accounting software to be a patchwork of programs written by long-departed summer students. Somehow, the hodgepodge worked well enough to be ignored. Looking at the mixture of programs, I found the software in Assembler, Fortran, and Cobol, the most ancient of computer languages. Might as well have been classical Greek, Latin, and Sanskrit.
As with most home-brew software, nobody had bothered to document our accounting system. Only a fool would poke around such a labyrinth without a map.
Still, here was a plaything for the afternoon and a chance to explore the system. Dave showed me how the system recorded each time someone connected to the computer, logging the user's name, and terminal. It timestamped each connection, recording which tasks the user executed, how many seconds of processor time he used, and when he disconnected.
Dave explained that we had two independent accounting systems. The ordinary Unix accounting software just stored the timestamped records into a file. But to satisfy some bureaucrat, Dave had built a second accounting system which kept more detailed records of who was using the computer.
Over the years, a succession of bored summer students had written programs to analyze all this accounting information. One program collected the data and stashed it into a file. A second program read that file and figured how much to charge for that session. Yet a third program collected all these charges and printed out bills to be mailed to each department. The last program added up all user charges and compared that total to the result from the computer's internal accounting program. Two accounting files, kept in parallel by different programs, ought to give the same answer.
For a year, these programs had run without a glitch, but weren't quite perfect this week. The obvious suspect was round-off error. Probably each accounting entry was correct, but when added together, tenths of a penny differences built up until an error of 75 cents accumulated. I ought to be able to prove this either by analyzing how the programs worked, or by testing them with different data.
Rather than trying to understand the code for each program, I wrote a short program to verify the data files. In a few minutes, I had checked the first program: indeed, it properly collected the accounting data. No problem with the first.
The second program took me longer to figure out. In an hour I had slapped together enough makeshift code to prove that it actually worked. It just added up time intervals, then multiplied by how much we charge for computer time. So the 75-cent error didn't come from this program.
And the third program worked perfectly. It looked at a list of authorized users, found their laboratory accounts, and then printed out a bill. Round-off error? No, all of the programs kept track of money down to the hundredths of a penny. Strange. Where's this 75-cent error coming from?
0 Well, I'd invested a couple hours in trying to understand a trivial problem. I got stubborn: dammit, I'd stay there till midnight, if I had to.
Several test programs later, I began actually to have confidence in the mishmash of locally built accounting programs. No question that the accounts didn't balance, but the programs, though not bulletproof, weren't dropping pennies. By now, I'd found the lists of authorized users, and figured out how the programs used the data structures to bill different departments. Around 7 P.M. my eye caught one user, Hunter. This guy didn't have a valid billing address.
Ha! Hunter used 75 cents of time in the past month, but nobody had paid for him.
Here's the source of our imbalance. Someone had screwed up when...