What is a Denial-of-Service attack?
Denial of Service (DoS) means an online attack that aims to prevent the legitimate usage of a website. The most common DoS method is flooding the targeted website with such a high volume of traffic that, in practice, the website is unable to serve its customers.
Distributed Denial of Service (DDoS) refers to an attack originating from multiple botnet sources against the targeted website, which is flooded with tens of gigabytes.