Those who are aware of the news on the internet, news linked to Anonymous, their actions, they will know that they have kept websites such as the FBI, CIA, US Department of Justice, and many other important sites (Interpol, Vatican, etc.) offline for several hours... not to make the story too long 
Just a few days ago the news came out that the administrators of the popular website Taringa are accused and will face "justice" in a trial. And actions by Anonymous They did not wait, because they quickly went offline (through DDoS attacks) various government sites from Argentina.
But… What is a DDoS attack?
I will explain it as simple as possible 
Attack DDoS means attack of Denial of Service. And in short, it is about accessing thousands of thousands of times to a website. In other words, if you or I now enter X site, this generates a certain load (it puts the server where the site is to work) ... 100 or 1000 people accessing the same site will generate a load greater than 10, that is logical. Well, DDoS attacks are the equivalent of hundreds of thousands (millions) of users accessing the same website PER SECOND. That is, 100.000 supposed users access, but after 1 second more are added ... and more and more per second. consequences? ... simple, there will come a time when the workload of the server (where the website is) will be so much, but SO MUCH, that it simply runs out of RAM, and can not do anything else ... and this my friends, will make the website goes offline.
I tried to explain it as simple as possible lol. That's why maybe the more knowledgeable ones will find some mistakes or details that have been left out, my apologies for this 
Now, here I will teach you how to do those attacks DDoS, using a tool developed by the same Anonymous: LOIQ.
Yes ... exists LOIC, meaning Low Orbit Ion Cannon, and can be used on Windows, Mac or Linux. The problem is that to use it in Linux, you need to install Wine and in this (in Wine) the Windows Net.Frameworks. That is, to make it work in Windows you need to emulate the LOIC (.exe) in our distro. Another way (which I haven't tried) is using Mono libraries.
I personally don't like either of these two alternatives. I don't really like using Wine, and I really hate Mono ¬_¬… so what to do in this case?
Fortunately, there is a version of LOIC call LOIQ (change from C to Q) written in C++ … and uses Qt libraries 
Simply put ...
We just go down a .tar.gz, we unzip it, and we just run the loiq file and BINGO !! we have LOIQ (which is the same as LOIC) opened in our distro, and ready to use  … or!! … you can simply install a .deb and ready 
Here are the download links:
LOIQ (Low Orbit Ion Cannon in C ++ and Qt) -" Archive .DEB
LOIQ (Low Orbit Ion Cannon in C ++ and Qt) -" Archive .TAR.BZ2
I directly use the .tar.bz2, because this way I save having to install another package as such on my system.
That is, for me to execute it, I download the .tar.bz2, unzip it, and execute.
I will leave you a command that will do the following:
- Download the .tar.bz2 package
- Unzip it.
- And it will allow you simply by typing in a terminal «loik»(Without the quotes) have the application run for them.
cd $HOME && wget http://ftp.desdelinux.net/loiq-0.3.1a.tar.bz2 && bzip2 -dc loiq-0.3.1a.tar.bz2 | tar -xv && mv loiq-0.3.1a .loiq-0.3.1a && sudo ln -s $HOME/.loiq-0.3.1a/loiq /usr/local/bin/
They will be asked for their password, they write it down and press [enter], and that's it 
Open another terminal and type «loik»(Without the quotes) and press [enter], the following should appear:
And that is LOIQ ... which is neither more nor less than LOIC but for Linux, using Qt libraries.
To do an attack (I will do a test with an internal server of my work), in the 1st field where it says URL we put the domain (for example, server.domain.com), or if we know the IP we can put this in the field below, the one that says IP. Once the data has been written in one of these two fields, we press the button to the right of the field that says «lock on«. Next, below and in the center it says 10 and below «Threads«, Increase this to any number, I will put 100. This number will be the number of packages / requests that will be made, and right next to (above where it says Method) we select HTTP in the drop-down list. They have many more options, timeout, directory they want to attack, etc. etc.
Since we are doing a test only, let's just leave that at that. I leave the screenshot of how it turned out for me:
And then, once the data is in ... they just press the largest button, the one with a lot of weird letters hahaha (says: IMMAH CHARGIN MAH LAZOR) … and the attack begins 
I'll do it here, and in less than 5 seconds the server I'm attacking (I remember, a server from here at work) will have almost 100% of the RAM occupied, and the CPUs at maximum… see:
As you can see ... 4CPUs (physical, not virtual), and 2GB of RAM went to the ground, offline server, no website of those that were there opened, POP3 service, IMAP service, everything was put offline, because the server had no more resources to respond to requests that were made.
And remember, this was only done by 1 person (I, a single LOIQ / LOIC) and with only 100 requests ... Can you imagine more than 3000 people doing DDoS attacks on the same server? (real figure ...) … as I said, even the CIA and FBI have succumbed 
I clarify, that this tutorial is with EDUCATIONAL PURPOSES!!
The objective of putting this tutorial is that just a few hours after being published, we will put another tutorial on iptables and how to gain protection against DDoS. That's the only reason we put this tutorial 
Other information to take into account ...
If you are going to do DDoS (which I don't tell you to do hahaha), I recommend that you first read the Anonymous security guide, there they explain about VPN and others.
Anyway. I hope you are good and don't use this for harmful purposes... don't let the dark side absorb you 
regards