DDoS (distributed denial of service)
DDoS attack · DoS · denial of service · flooding attack · volumetric attack · déni de service
An attack that knocks a website or service offline by flooding it with requests sent simultaneously from thousands of machines.
In practice
A DDoS steals nothing: it blocks. Volumetric attacks saturate bandwidth, while others exhaust a server’s or application’s resources with requests that look legitimate. They are launched from botnets or bought from online services, by extortionists, hacktivists or unscrupulous competitors. Protection is mostly about preparation: DDoS mitigation is arranged before an attack, not during one.
During the Paris 2024 Olympic and Paralympic Games, ANSSI handled 548 cybersecurity events. Nearly half involved service unavailability, with DDoS attacks accounting for a quarter of those; none disrupted the ceremonies or the competitions.
How to protect yourself
- Subscribe to DDoS protection (from your host, network operator or content delivery network) and test it.
- Identify vital services and plan a degraded mode of operation.
- Prepare emergency contacts (host, operator) and a customer message in advance.
- Do not expose the real IP address of protected servers.
