Non-fiction, computer hacking, clue was a few cents of computer time used

I read this paperback true tale in the 1980s, I think. It was after the Internet, but before the World Wide Web. It was told about a person who noticed that the time being billed on the computer he was in charge of (in some capacity) was just a few cents off. And every month it was a few cents off. And through that clue, he determined that his system had been hacked, and that quite a few other systems had also been hacked. And now I cannot think of the name of the book.

Help!
EowynA

Possibly The Cuckoo's Egg by Clifford Stoll.

Yes, yes!!!! That is it! Got it in one, and so quickly!

Thank you very much. Now I know what book I am searching for on my shelves.

You're welcome!

Yep, I knew it too, right off. One of my favorites - I've read it half a dozen times. He's good.

I read this book too and seeing this thread has me wanting to reread it whenever I dig it out of where it may be. Back when I read it, it was a "group read" for a bunch of us on one of the message boards I hung out on at the time, and we even managed to get Cliff to come in and talk with us about it!

6> Oh, that would be fun! Yeah, it's started niggling at me to be reread again, now that I've been reminded of it...