The slow loris is a kind of slow and low attack invented by RSnake in 2009.

Can I send requests so slowly, that I just bore them to death? And the answer is yes, yes you can! The idea of a slow loris attack is very simple. This marks the end of the headers, allowing the server to process the request the moment it receives this empty line. This conversation will continue back and forth until we load the page and all of its assets.ДЄ sample HTTP/1.1 GET request header will look like that:Д®nter fullscreen mode Exit fullscreen mode And the server will send us the file we requested. Then we will send a new GET request and we will say 'Hey I need logo.png now'. We will send a GET request to the website, and we say 'Hey I want index.html'. Now let's make a quick and dirty recap on how HTTP/1.1 GET requests work. Server - Client Communication with HTTP/1.1 Since such attacks use legitimate requests traditional firewall filtering rules do not play well. Such a kind of attack is very difficult to mitigate, especially for smaller organizations with limited infrastructure. If you don't, it will just laugh in your face. If you manage to send enough the machine will go down. As many requests as possible all at the same time. Some modern attacks use techniques such as DNS amplification in order to maximize the impact of the attack.Д«ut the main idea behind a DoS attack remains the same. Here instead of a single computer, you utilize a bunch of them in order to simultaneously send as many requests as possible to the machine on the other side. Since the machine has a finite amount of resources, if you manage to send more requests than it can handle, the server will go down.ДЄ distributed denial-of-service or DDoS attack, is the next level. The idea behind this attack is that you are trying to crash the machine that is on the business end of this attack, by sending as many requests as possible. In order to understand how such an attack works, let's refresh some basics ( too bored, show me now)ДЄ denial-of-service or DoS attack is an attack in which the attacker, seeks to make a machine or network unavailable to its intended users by disrupting the services of the host, either temporarily or indefinitely. Slow loris is a denial of service attack that can wreck havoc in unprotected thread-based web servers such as Apache, created in 2009, by a guy named RSnake (and is one of my favorite DoS attacks рџ†)

However, when setting such restrictions, it is important not to forget the risk of blocking legitimate users attempting to connect to the server from behind a NAT, or via slow or unstable channels.The cover image is a real life slow loris. The simplest protection measure against this type of attacks is to reduce time out set for waiting for a response packet and restrict the number of cached sessions from the same address or subnet. A special type of such an attack is called SlowLoris, during which the HTTP sessions with victim web-server are kept open. Botnet-generated session attacks come from real IP-addresses, and to initialize the TCP session, the вЂњTCP 3-way handshakeвЂќ is carried out. Due to the increasing number of fake sessions, fewer and fewer system resources are left to maintain and open new TCP sessions with legitimate users, and, consequently, the victim server becomes inaccessible. As a result, the victim server allocates available resources to maintain the open TCP sessions with bots. Empty session consumes system resources (RAM, CPU, etc.) that are allocated by the server in order to process the open session.

When the session has been successfully established, the attacker's bot does not respond with ACK packet to keep the session open until session time out occurs. TCP session is established between the bot and the victim server.

Slowloris attack scope