Suggest an editImprove this articleRefine the answer for “What is DDoS?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**DDoS (Distributed Denial of Service)** is an attack aimed at making a service or website unavailable by overwhelming it with a huge number of requests from many sources. **Key point:** the main difference from DoS is that the attack comes from many devices at once, making the source hard to trace and block.Shown above the full answer for quick recall.Answer (EN)Image**DDoS (Distributed Denial of Service)** is an attack aimed at **making a service or website unavailable** by overwhelming it with **a huge number of requests from many sources**. In simple terms: *thousands or millions of requests "pile onto" the server at once, and it stops responding to normal users.* --- ## The essence of DDoS Every server has limits: - on network bandwidth; - on the number of connections; - on CPU and memory. A DDoS attack **exhausts these resources**, so that: - the site does not open; - the service works very slowly; - connections drop. The main difference from DoS is that **the attack comes from many devices at once**. --- ## Why DDoS is called "Distributed" **Distributed** means "spread out." The attack comes: - from a botnet (thousands of infected computers); - from servers; - sometimes from IoT devices (cameras, routers). That is why the source of the attack is hard to trace and block. --- ## Main types of DDoS attacks ### 1. Volume-based (L3/L4) **Goal:** to clog the communication channel. Examples: - UDP flood; - ICMP flood. The network becomes overloaded. --- ### 2. Protocol attacks (L3/L4) **Goal:** to exhaust the resources of network devices. Examples: - SYN flood; - Ping of Death. The protocol stack becomes overloaded. --- ### 3. Application (L7 DDoS) **Goal:** to overload the application itself. Examples: - HTTP flood; - mass requests to an API. The hardest to detect, they look like ordinary users. --- ## What DDoS violates - **Availability**, one of the key security principles. Data is usually not stolen or altered, the service simply "goes down." --- ## How to defend against DDoS ### Main defense measures: - rate limiting; - firewall and traffic filtering; - anti-DDoS services; - CDN and load balancing; - Anycast. Serious DDoS attacks are usually defended against **at the provider or cloud level**.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.