So, many have reported the BBC DDoS attack end January 2015 to be the largest ever at 602 Gbps. Many sites just spread that info without bothering to find out how they came to that number.
It turns out that number may well be exaggerated as there was no trace reported of such magnitude.
Here is a lengthy article that sums it all up rather well, without many technical details. Just crosschecking what the hackers ("The New World Hackers") claim, with that feedback obtained from Amazon, Arbor, BBC.
▻http://www.zdnet.com/article/tango-down-bbc-was-this-the-largest-ddos-web-attack
Some publications were quick to capitalize on the news of the “biggest-ever” web attack. Some hedged their bets in the face of a lack of evidence.
But the absence of convincing proof, coupled with a barrage of misleading statements, suggests that the biggest web attack in living history was — for all intents and purposes — nothing more than a publicity stunt from a faceless group.