DDoS Attack: Explained

Denial of Service Attack

Denial of Service Attack (Photo credit: kryptyk)

I try to explain what terms and acronyms mean as a way to educate our readers. In that light, Zen Technologies has written a guest article on one such term they know a lot about: DDoS attacks.

What is a DDoS attack?

DDoS stands for Distributed Denial of Service. As the name suggests, a DDoS is typically launched from a distributed network of computers, and may be coordinated by one computer. By overloading the target computer or network with requests to access some part of it, the computers carrying out a DDoS may be able to overwhelm the target system. As a result, the target computer or network’s resources are totally consumed by its attempts to respond to these requests and the target is consequently unable to carry out its routine tasks. This means that its users are denied the services which it usually provides. Credit card and bank websites have been the targets of such attacks in the past, and this has resulted in their customers being unable to use their pages. While some DDoS attacks have been coordinated by internet ‘hacktivist’ groups such as Anonymous, others have been directed by businesses hoping to disable their rivals’ businesses operations.

DNS Amplification – A new method of DDoS

A recent attack on the website of anti-spam service Spamhaus resulted in a substantial slowdown in European internet speeds. This particular attack was highly effective because it exploited part of the internet’s infrastructure called DNS (Domain Name System) servers. These servers take human-readable website addresses which a computer sends them and return them to the computer as machine-readable addresses. This process is called a DNS look-up. If the look-up request is fairly general, the response that is generated by the server can end up being as much as 60 times larger in size than the initial request. The coordinators of the Spamhaus attack did exactly that, with one crucial variation. Generating a massive number of DNS requests would ordinarily have meant that the responses were returned to the attacker. Instead, the attackers of Spamhaus and others seeking to carry out a DNS Amplification attack used what was effectively a fake return address. As a result, all of the attackers’ DNS look-up request responses were directed towards the Spamhaus servers. This meant that Spamhaus was bombarded with requests to access its servers far in excess of what a normal DDoS attack. The use of DNS servers allows attackers to amplify the power of their attacks. This is the general principle underlying DNS amplification attacks

About DDoS Protection and Zen


Zen Network Technologies mitigates DDoS attacks all over the world. Let’s make the web a safe place. Feel Zen, be Zen.

Be very careful…it’s dangerous out there.

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Best regards,



I’m also on Twitter, @PaulsInternet.

Images courtesy of FreeDigitalPhotos.net and FreeByte.com



Filed under Cybercrime, Education, Internet Security, malware

4 responses to “DDoS Attack: Explained

  1. Pingback: Distributed Denial of Service Against U.S. Banks and Government Websites | Cybersecurity Law Blog

  2. Pingback: Building A Web Site Has Never Been Easier | What's On My PC

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