Distributed Denial-of-Service (DDoS) is a big threat to the availability of Internet-based services today. Low rate DDoS attacks, especially pulsing attacks, aim to degrade the Quality of Service experienced by users by using only a small amount of attack traffic, unlike conventional volume-based DDoS attacks. To improve the effectiveness and stealthiness, these pulsing attacks assume that the attack packet is concentrated on the server in a very short time (a few milliseconds) using state-of-the-art synchronization techniques. However, even with the most advanced technology in the real world, it is almost impossible to achieve this tight level of synchronization, which means the effectiveness of the pulsing attack can be overestimated based on the exceeded assumption. In this paper, we use the Very Short Intermittent DDoS attack (VSI-DDoS) as an example to measure the practical effectiveness of a pulsing attack in a realistic environment. We found that VSI-DDoSbecame substantially less effective. That is, it lost 85.7% in terms of effectiveness under about 90ms synchronization inaccuracy, which is a very small inaccuracy under normal network conditions.

分布式拒绝服务（DDoS）对当今基于Internet的服务的可用性构成了巨大威胁。与传统的基于卷的DDoS攻击不同，低速率DDoS攻击（尤其是脉冲式攻击）旨在通过仅使用少量攻击流量来降低用户体验的服务质量。为了提高有效性和隐身性，这些脉冲式攻击假定使用最先进的同步技术，将攻击包在非常短的时间内（几毫秒）集中在服务器上。但是，即使使用现实世界中最先进的技术，也几乎不可能达到这种严格的同步水平，这意味着可以根据超出的假设高估脉冲攻击的有效性。在本文中，我们以非常短的间歇性DDoS攻击（VSI-DDoS）为例，来测量实际环境中脉冲攻击的实际效果。我们发现，VSI-DDoS的有效性大大降低。也就是说，在大约90ms的同步误差下，它的有效性损失了85.7％，这在正常网络条件下是很小的误差。