Today, botnets are still responsible for most large scale attacks on the Internet. Botnets are versatile, they remain the most powerful attack platform by constantly and continuously adopting new techniques and strategies in the arms race against various detection schemes, . Thus, it is essential to understand the latest of the botnets in a timely manner so that the insights can be utilized in developing more efficient defenses. In this work, we conduct a measurement study on some of the most active botnets on the Internet based on a public dataset collected over a period of seven months by a monitoring entity. We first examine and compare the attacking capabilities of different families of today’s active botnets. Our analysis clearly shows that different botnets start to collaborate when launching DDoS attacks.