If he could somehow work out the algorithm that the serial numbers follow. The software or server only knows that a serial number is correct by either : 1) It

If he could somehow work out the algorithm that the serial numbers follow. The software or server only knows that a serial number is correct by either : 1) It matches an algorithm Ie, if your algorithm was 'all even numbers' are correct serials, then if your boxes had the numbers 100, 102, 104 then it may be obvious that 106 would be a correct serial number. 2) The software connects to the software creators server to verify a random serial number on the box is stored in their database and hasn't been activated before. To get around this, you could either hack the server and copy their database or intercept the response from the server to the application and emulate this response that indicates 'yes this is a valid serial'. Though I think your character would sound cooler if he did #1 :)