The attack on the unnamed organisation and its DNS provider happened between 5 and 12 November and reached 45Gbit/s at peak, equivalent to 69 million packets or 15,000 connections per second, way above the level that can be easily stemmed using standalone appliances, the company claimed.
The assault was sustained over nearly eight days in four different waves, focussing on the vulnerable application layers, a clear attempt to knock the business offline.
"This attack was three times larger in packets per second volume than the biggest attack Prolexic has mitigated previously, which also occurred in 2011" said Prolexic CTO, Paul Sop.
What is new is that the attackers had tried to hit the DDoS defences, which suggests sophistication; attackers assumed that the organisation would have some defences in place that needed to be overcome.
The company's latest analysis of DDoS attack trends for Q3 2011 found that while year-on-year the total number of attacks had decreased, the size of the attacks was growing, with attackers sometimes wielding the huge power of the recent November attack.