Examples of DDoS attacks

In UDP reflection attacks, an attacker can spoof the source of a request and use UDP to elicit a large response from the server. The extra network traffic directed towards the spoofed, attacked IP address can slow the targeted server and prevent legitimate end users from accessing needed resources.

The intent of an TCP SYN flood attack is to exhaust the available resources of a system by leaving connections in a half-open state. When a user connects to a TCP service like a web server, the client sends a TCP SYN packet. The server returns an acknowledgment, and the client returns its own acknowledgement, completing the three-way handshake. In a TCP SYN flood, the third acknowledgment is never returned, and the server is left waiting for a response. This can prevent other users from connecting to the server.

In a DNS query flood, an attacker uses multiple DNS queries to exhaust the resources of a DNS server. Amazon Shield Advanced can help provide protection against DNS query flood attacks on Route 53 DNS servers.

With an HTTP flood, including GET and POST floods, an attacker sends multiple HTTP requests that appear to be from a real user of the web application. Cache-busting attacks are a type of HTTP flood that uses variations in the HTTP request's query string that prevent use of edge-located cached content and forces the content to be served from the origin web server, causing additional and potentially damaging strain on the origin web server.