# disables keep-alive when 180 (70%) TCP connections are occupied # limit maximum number of active TCP connections limited to 256 # handle connections from up to 100000 different IPs This is not a problem at all when there are more than x request at the same server from real persons as long as their connection isn't working in the same way the Slowloris attack does, so if your application has access from more users than the specified at this property, they will be able to access it as long as it's not a Slow HTTP request. This will prevent automatically an user from creating more than x requests (specified at QS_SrvMaxConnPerIP) at the same time from the same device/network. To describe shortly what we are doing, is limiting the number of simultaneously inbound connections from a single IP. This will open the conf file of the module on the editor, here you need to change it's content to the following one, optimize and change these values according to your needs: Nano /etc/apache2/mods-available/qos.conf The installation of the module will create a configuration file that is stored in the mods-available directory of apache, you can edit it quickly with nano using: # Edit the qos.conf file with your favorite terminal editor, we'll use nano So you can enable/disable it dinamically with just a checkbox on the graphic user interface of Plesk.
For Plesk based serversĪfter the installation of the module through the command line, the module registers and activates itself automatically, so if you try to access the apache settings on a Plesk based server, you will see the extension on the list: Penetration of the web server by attackers (DoS).įor more information about the mod_qos module of Apache, please visit the official website at SourceForge here.Oversubscription of link capabilities due to many concurrent clients uploading or downloading data.when request processing includes time consuming database queries.
Quality of service implements control mechanisms to provide different priority to different users, applications, and data connections.
Install mod_qos moduleĪs first step, access your server through the terminal, update the repositories and install the module with the following command: # Update reposĪfter installing the module, it will register and enable itself automatically.
In this short article, we will explain you how to install and configure the QoS module of apache in your Ubuntu 16.04 server. This package is available in the Ubuntu repositories so it should be pretty easy to install and configure on this environment. mod_qos provides you with some opportunities to scale the number of used connections on your server to defend it from the attack according to the bandwith limits. This kind of attack does not consume a lot of resources or bandwith at all.The load-impact is pretty low, however the http(s) services quits serving really fast. Some servers may have a smaller tolerance for timeouts than others, all depends of your configuration, but the algorithm can compensate for that by customizing timeouts.
This algorithm is designed so that a single machine (Linux/Unix based machine since Windows limits how many sockets you can have open at any given time) can easily tie up a typical web server or proxy server by locking up all of it's threads as they patiently wait for more data. One of the most known and easy to implement, is the Slowloris attack. There are a lot of attacks that can be performed to a server when it's not correctly configured or doesn't expect such kind of attack at all.