A Slowloris attack is a form of a "Low-and-Slow" attack that aims to overload a web server and prevent access to it by tying up all available connections to the server. In a Slowloris attack, the attacker sends many HTTP requests to the server, but does so extremely slowly by intentionally delaying the data transfer.
Typically, the attacker opens many connections to the server and keeps them open by sending only part of the request and then leaving the connection open by sending additional parts of the request slowly or simply not sending any further data. This way, all available connections to the server are tied up, preventing legitimate users from establishing a connection since there are no free connections available.
This attack is particularly effective against web servers that do not enforce a limited number of connections per user or IP address and rely on the server's resource availability to serve requests. However, a well-configured web server can detect and mitigate such attacks.
