Brainjack: the next war starts in cyberspace, by Brian Falkner

Sam Wilson, brilliant teenage hacker, is looking for trouble. And trouble is looking for him. He's trying to get into the most carefuly controlled pieces of cyberspace there is - but he has no idea of the danger that he's getting himself into, it's not just that the police might be after him, he's being chased by an agency he can't even comprehend.
Ok, I'm a science fiction buff, so nothing in this book was particularly new, but it didn't seem to matter, it was a great roller-coaster. Lots of fun, lots of danger, and some really nice touches -- it makes me want to read his other book - the tomorrow code - to see if it's half as good as this one.

About the author:  I'm slow on the uptake (my excuse is that the book was published in Aus):  Brian is actually an NZ author -  born and raised in Auckland - which I wont hold against him, and is the author of several aother books besides this and the Tomorrow code (shortlisted for the 2009 New Zealand Post Book Awards for Children - Young Adults and the Esther Glen Award at the LIANZA Awards). The Flea Thing (shortlisted for the LIANZA Esther Glen Award, 2004), The Real Thing, and The Super Freak (shortlisted, New Zealand Post Book Awards, 2006).