HTTP Flood

HTTP Flood is a type of DDoS attack that belongs to the application-layer attacks family. During the attack, the attacker sends an HTTP GET or POST requests to an application or a web server. Newer techniques abuse HTTP/2 itself, such as the HTTP/2 bomb attack, where a tiny request can freeze a web server.

The requests sent seem legitimate containing a valid header and a correct and complete message. However, the message body sent at an extremely slow rate is what causes the targeted server to try to obey it for a very long time. Sending a large number of these requests, each establishing a connection, makes other legitimate incoming connections impossible. By contrast, network-layer floods such as the ACK flood and the UDP flood do not involve application requests. A similar flood of requests aimed at DNS servers is the DNS query flood.

Notes:

• This attack does not require a large bandwidth to bring the target down. However, it requires understing the targeted application or site.
• The legitimacy of the requests sent makes the attack harder to detect and block.