In the past, computer intruders have been motivated by intellectual curiosity and a desire to understand the PSN. Today, computer intruders are discovering that they can sell their services and are motivated by greed. The report ``The Electronic Intrusion Threat to NS/EP Telecommunications'' notes the following about fraud and financial loss [19]:
Toll fraud is a multibillion-dollar-per-year business in the United States. Normally, the toll fraud threat is not seen as being related directly to the performance of Government agencies' ability to perform NS/EP missions. Because of the nature of this threat, toll fraud should be considered a significant problem, but one with undefined NS/EP implications [19].