DoS and DDoS attacks: What are the differences?

The Internet is one of the biggest revolutions in modern human history. It has changed the way we live and communicate. But like everything, there’s a downside to the Internet too, and those are cyber attacks. The nature of the Internet and its ability to transmit data among entities located in different parts of the world also make it a hunting ground for hackers looking to steal data and information that passes through the Internet and use them for personal gains. Hackers come up with different ways to steal data from the Internet, and two of the prominent attacks that we will talk about today are DoS and DDoS. Though it may seem like only a single letter separates the two attacks, in reality, these attacks are very different.

What is a DoS attack?

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Denial-of-service (DoS) is a cyberattack where a hacker interrupts a computer, server, or any other device and makes it unavailable to users.

In this attack, the hacker floods a device with so many requests that its resources become insufficient for normal functioning. As a result, the device becomes unavailable for users. However, the hacker uses only a single computer to send these requests and attack the target device.

Types of DoS attacks

There are two broad types of DoS attacks — buffer overflow and flood.

In a buffer overflow attack, a single computer sends many requests to a device, and these requests consume the available memory, CPU, and hard disk space. As a result, the attacked system crashes or slows down and even becomes unavailable to service genuine requests.

On the other hand, a flood attack is when a hacker oversaturates the server capacity, resulting in a DoS attack. In this attack, the hacker must have more bandwidth than the attacked system to send a continuous stream of data packets for handling.

In general, if your system slows suddenly, takes a long time to open files or websites, loses connectivity, or exhibits any such behavior, it could indicate a DoS attack.

What is a DDoS attack?

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A distributed denial-of-service (DDoS) attack is where a hacker overwhelms a system with a flood of Internet traffic.

Since it is impossible to use a single system for sending so many requests, a cybercriminal uses many compromised devices to send packets/requests to a system. When the attacked system is unable to service all the requests, it crashes and becomes unavailable for real requests.

The best way to identify a DDoS attack is through a detailed traffic analytics report. In general, you can suspect a DDoS attack when high amounts of traffic are coming from a single or a small range of IP addresses. Also, unexplained surges, especially at odd times, can indicate a DDoS attack.

Types of DDoS attacks

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Like the DoS attacks, the DDoS attacks can be of different types too.

  • Layer 7 attack: Attacks the application layer of the OSI model. Typically, web page requests are flooded to exhaust the target’s resources, resulting in a denial of service to legitimate requests.
  • Protocol attacks: These attacks over-consume the server’s or a network device’s resources and typically happen in layers 3 and 4 of the OSI model.
  • Amplification attacks: These attacks consume all the available bandwidth and create congestion, so genuine requests can’t go through.
  • Teardrop Attack: In this attack, infected systems inject fragments of IP data packets, and the network exhausts all its resources in trying to recompile those fragments.
  • SYN Flood: This attack exploits the TCP handshake model where a system waits for another one to respond. Initially, a flood of packets is sent to the target machine, but the final step of the handshake doesn’t happen. As a result, the target machine keeps waiting for the final handshake and exhausts its resources.

On the surface, a DoS and a DDoS attack may seem similar, but in reality, they are vastly different. Let’s see how.

Differences between a DoS and a DDoS attack

A key difference between DoS and DDoS is the number of devices used for the attack. While a DoS attack uses only one system, a DDoS attack sends requests from multiple systems.

Some of the other differences are as follows.




Detection Easy to detect the origin of the attack, so you can sever the connection right away Hard to detect because it comes from multiple systems with spoofed IP addresses
Pace Relatively slow as only a single system has to fire all the requests. The pace is limited by the system’s capabilities Extremely quick since packets can be fired instantly from multiple devices
Level of damage Low to moderate Moderate to catastrophic
Use of botnets Extremely rare. Hence, detecting a single source is easy Common, so tracing the origin is complex and time-consuming
Execution Simple, as it involves only a single system or script Involves complex coordination of infected botnets and systems
Volume of Traffic Comparatively lesser than DDoS High
Mitigation Quick to mitigate as you can quickly disconnect the target system from the attacker It will take some time to recover from the attack and may require advanced tools. Often, the results are highly impactful

In all, a DoS attack emanates from a single system and hence is easy to detect and contain while a DDoS emanates from a bunch of infected botnets controlled by a commander system. Hence, these attacks are hard to detect and are impactful.

How to protect from DoS and DDoS attacks?

The good news is there are many ways to thwart both DoS and DDoS attacks.

Here are some suggestions.

  • Update your system with the latest patches and security measures to prevent it from becoming a botnet in an attack.
  • Review logs regularly to identify attack patterns.
  • Implement strong password policies and strengthen the authentication process.
  • Monitor your network continuously for abnormal traffic patterns.
  • Run DoS and DDoS simulation tests to identify vulnerabilities in your system.
  • Create a backup and disaster recovery plan. As a part of this plan, pinpoint accountability and response parameters.
  • Take additional measures for critical systems.
  • Provision extra bandwidth when needed, so you can get some more time to recover from the attack.
  • Implement a comprehensive security strategy and audit to prevent these attacks, and to mitigate them at the earliest when needed.

Often, you need to implement two or more of the above strategies to combat DoS and DDoS attacks.

We hope this helps you to understand the differences between a DoS and a DDoS attack.

If you’ve faced either or both of these attacks, please tell us how you mitigated them and what security strategies you have put in place to avoid them in the future. Your valuable experience is sure to help our readers stave these deadly attacks.

Featured image: Shutterstock

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