Computer Crime Definition
A computer crime is any illegal action where the data on a computer is accessed without permission. This access doesn't have to result in loss of data or even data modifications. Arguably the worst computer crime occurs when there are no indications that data was accessed.
Computer crime is often attributed to rogue hackers and crackers, but increasingly organized crime groups have realized the relative ease of stealing data with relative low-level of risk. Government organizations are also rumored to be involved with hacking in to computer systems, but the legality of such actions is far too grey an area to be discussed here.