"When the massive distributed denial-of-service (DDoS) attack in March brought down the voice-over-IP (VoIP) call processing supplied by TelePacific Communications to thousands of its customers, it marked a turning point for the local-exchange services provider in its thinking about security .. The attack resulted in widespread service disruptions for a number of days in late March and cost the company hundreds of thousands of dollars in customer credits"
".. TelePacific sees a multitude of daily scans against its network, and low-level attacks can occur about twice a day. But the services provider had never before seen what happened in the March period when the normal level of 34 million SIP traffic registration requests for VoIP connections suddenly shot up to 69 million and "flooded our systems .. There was no calling ability .. even installing Arbor's PeakFlow anti-DDoS equipment isn't the complete answer to the problem because when DDoS attacks are strong enough, PeakFlow can't necessarily stop the worst of them".
Stacy M. Arruda, an FBI agent was there as well, saying that "many cases of network attacks which the FBI works on do appear to involve a financial motive"
See "Massive DDoS attacks a growing threat to VoIP services" - here