# Under a DDoS attack?

A distributed denial-of-service (DDoS) attack is where a large number of computers or devices, usually controlled by a single attacker, attempt to access a website or online service all at once. This flood of traffic can overwhelm the website's origin servers, causing the site to slow down or even crash.

sequenceDiagram; participant User; participant Website; participant Server; participant Botnet; User->>Website: Requests to access site Website->>Origin Server: Processes user requests Botnet->>Origin Server: Sends a flood of traffic Origin Server-->>Website: Slows down due to traffic overload Origin Server-->>User: Unable to respond to user requests

Common signs that you are under DDoS attack include:

- Your site is offline or slow to respond to requests.
- There are unexpected spikes in the graph of
**Requests Through Cloudflare**or**Bandwidth**in your Cloudflare**Analytics**app. - There are strange requests in your origin web server logs that do not match normal visitor behavior.