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Denial-of-Service (DoS) Attack - What is, Types, and Prevention

Denial-of-Service (DoS) Attack - What is, Types, and Prevention

Through this blog, you will understand the following concepts of a DoS attack.

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What is a DoS attack?

The term Denial of Service attack is quite common. If you are wondering what is a DoS attack?, this section will help you to understand the same.

As the name suggests, when an online service is denied due to attacks, then it is known as a Denial of Service attack. Usually, the attack comes in the form of mass traffic.

What does the traffic do? When you try to access a site, the attacker usually sends large traffic making the site inaccessible for you.

You might wonder, isn’t traffic good for sites? Yes, traffic, in general, helps in increasing the revenue of the sites. But when traffic is generated with malicious intent to disrupt the organic traffic, it will be harmful to the sites.

A Denial of Service attack usually happens to crash a site with overwhelming traffic.

The massive bot traffic, which attacks the network, does not usually carry any return address. In this way, when the site host tries to authenticate the address, it will cause an error. As it takes time to resolve such an error, the attacker will be ready to launch another DoS attack on the site.

But, what is the purpose of a denial of service attack?

It is important to note that the target of a DoS attack is not a security breach. The main target of a DoS attack is to, usually, cause revenue loss, toy with an organization’s reputation, and other such things. In addition to the mentioned motives, other motivations include extortion, personal rivalry, cyberwarfare, business competition, and more.

Based on your understanding of what is denial-of-service attack, you might wonder if there are any popular denial-of-service attack examples. Following are a few of the most popular DoS attacks in history.

Ping flood DoS attack:

This type of DoS attack is also used as a DDoS attack. This is a DoS attack where traffic level beyond the site’s processing or hosting capacity is generated. Such traffic is generated through ICMP ping packets.

The advanced level of ping flood DoS attack is known as the ping of death. This Denial of Service attack results in a targeted system crash via a malformed packet sent to the network.

Smurf DoS attack:

The type of attack that utilizes a network address to flood an IP address is known as a smurf DoS attack. This is achieved via spoofed packets.

In addition to the above-mentioned attacks, other types of DoS attacks include teardrop attacks, email bombs, and more.

On understanding the historical examples of denial-of-service attacks, you might wonder if DoS attacks are currently existing. The answer is yes, and the following are the common types of DoS attacks.

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Common types of DoS attacks

Application-layer flood DoS attack

When a server is filled with spoofed IP address requests, it is known as the application-layer flood attack. The attack can happen with millions of attacks per second. This type of DoS attack functions with the motive to slow down or crash the service. The attack continues until the service’s processing saturation limit is reached.

Unintended DoS attack

Sometimes, a story might become popular on social media. In social media terms, such overnight sensational news is called viral.

Viral news or stories usually happen randomly. In that case, when a large population is trying to access a particular site, the site will crash due to limited capacity. Since small-scale sites are built with limited capacity, organic users will have trouble accessing them as well.

This type of attack that happens unintentionally, in the absence of malicious intent by a third party, is known as an unintended Denial of Service attack.

DDoS attack

DDoS attack stands for distributed denial-of-service attack. It is almost similar to a DoS attack. The major difference being that a Denial of Service attack happens from a single IP address in contrast to a DDOS attack that happens from multiple sources.

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Following is the comparison between DoS attack and DDoS attack.

Difference between DoS attack and DDoS attack

  • Denial-of-service attack is known for its acronym DoD attack. Distributed denial-of-service attack is known for its acronym DDoS attack.
  • A DoS attack happens from one IP address. A DDoS attack happens from multiple IP addresses.
  • Comparatively, a DDoS attack happens faster than a DoS attack.
  • A DoS attack uses a single device. A DDoS attack uses bots.
  • Comparatively, a DoS attack can be traced more easily than a DDoS attack.
  • The volume of attack is higher in a DDoS attack than in a DoS attack.

The above section stated what is a Denial of Service attack and how it is different from a DDoS attack. In the following section, you will be introduced to the common tools used in DoS attacks.

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Tools used in DoS Attacks


HULK is one of the popular DoS attack tools. It is used to generate unique requests in an unstable pattern. HULK attacks the server’s resource pool directly by using referrer forgery. Referrer forgery helps HULK to surpass cache engines.


XOIC is one of the DoS attack tools. It comes in test mode, normal Denial of Service attack mode, and DoS attack mode. The above-mentioned are listed chronologically based on the intensity level of their attack.


Low Orbit Ion Cannon (LOIC) is a free DoS attack tool. The free tool is very effective in DoS attacks. The basic requirement to perform an LOIC DoS attack is to know the site’s IP address; alternatively, the site’s URL address can be used as well.

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If you are wondering how to prevent DoS attacks, the following section will help you.

DoS Attack Prevention

After understanding what is a denial-of-service attack, you might wonder if there are any ways to prevent your site or organization from such attacks. The answer is, yes!

By preventing DoS attacks, you can save your organization from issues such as revenue loss and more. The following tips on how to prevent Denial of Service attacks may come in handy:

  • Deploy firewall: This will minimize the attack surface. However, this will be more effective if the firewall has a restrictive list.
  • Invest in anti-DoS tools: This will identify and filter attack traffic as anti-DoS tools are built with features that can differentiate organic and bot traffic.

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DoS attacks usually happen by generating mass bot traffic. Denial of Service attacks are usually generated for malicious intentions and, sometimes, they can happen unintentionally as well. Several DoS attack tools are available on the internet. It is recommended to install or invest in anti-DoS tools to prevent your site or your organization’s site from being subjected to DoS attacks and ensuring hassle-free user experience for your audience.

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About the Author

Technical Lead - AWS Solutions Architect

Shivanshu is a Technical Lead and AWS Solutions Architect passionate about utilizing Cloud technology to empower businesses. Proficient in AWS, Terraform, and GCP, he crafts innovative solutions to propel companies forward. As an enthusiastic writer, he shares his expertise to inspire others in this field.