A few weeks ago we noted that Belgium was going to the second position worldwide in the number of DDOS attacks that were taking place in the world. Some of that attacks were attributed to some configuration problems (malicious according to some because they make too much trafic and normal according to others who say you just have to drop it if you don't like it). But there seemed to be other sources as well.
So we contacted some sources and informed them about the information. THings seems to have become more quiet since than and Belgium is nowhere near the top DDOS attackers worldwide.
Just keep monitoring your own network and be sure that you have DDOS protection in place because one day you may need it. Some ISP's have DDOS protection in standby contracts that can be activated when needed. As a professional network or hoster you should have such a contract. Beginning from scratch in the middle of such a storm is not very wise. You can't treat at the same time the effects of the attack and the negotiations about the contract to filter all that traffic.