Types of DoS Attacks: Methods, Examples and Prevention

The internet fuels the everyday operations of modern businesses, but this connectivity also puts businesses at risk. Cyberattacks are rising every year, with an estimated 5.5 billion annual attacks.¹ One such attack is known as a denial of service (DoS) attack. DoS attacks involve flooding a targeted server with irrelevant requests to disrupt service to legitimate users.

These attacks resurged in 2024, partly because of a rise in internet-connected devices such as smart HVAC systems and internet of things (IoT) sensors.² As a cybersecurity professional, becoming familiar with different types of denial of service attacks will help you keep your company and its data safe. You can better identify potential threats and make strategies to prevent them. This post explores types of DoS attacks and outlines prevention strategies.

With the resurgence of DoS attacks, it helps to understand how they work. There are several common denial of service categories.

Volume-based attacks, which may also be distributed denial of service attacks (DDoS), involve flooding servers with an overwhelming number of requests that seem like legitimate traffic. One such method for committing this type of DoS attack is the use of a User Datagram Protocol (UDP).³

When your server receives a UDP packet, it checks for related applications. If your system can’t find one, it responds with an Internet Control Message Protocol (ICMP) stating that the destination isn’t reachable. While your server is researching and responding to all these spoof requests, your customers can't reach your website or app.

This type of DoS attack takes advantage of weak communication protocols within your network. These protocols govern how devices format, address and transmit data, including how your system processes email, file transfers and web pages.

A type of DoS attack known as a synchronized (SYN) request flood consumes various connections governing components of your system. A synchronized request happens whenever a client tries to access a network. To attack your system, a cybercriminal sends multiple SYN requests to open connections.⁴ These connections stay open, waiting for additional instructions, blocking legitimate users from accessing your servers.

Application layer DoS attacks target services at the app layer, such as your web server or firewalls. If successful, an application layer attack can effectively shut your website down.

To execute this type of denial-of-service attack, a cybercriminal will spoof client IP addresses and flood your system with anonymous HTTP requests. They also use botnets, which are malware-infected connected devices, to bog down your network.⁵

When your employees or customers try to access your server, they either experience slow loading speeds or can’t access your servers at all.

A zero-day attack is particularly dangerous because it involves an attacker taking advantage of an unknown flaw in your system.⁶ This can happen if you don’t regularly monitor your system and install patches. Since you’re unaware of the flaw until a hacker has already exploited it, you essentially have “zero days” to fix the issue.

Recently, the IT software company Kaseya experienced a ransomware attack by bypassing forgery protections in the company’s network.⁷ Many of the company’s customers had to take their systems offline. Swedish grocer Coop ended up having to close more than 500 locations while fixing the problem.⁸

During reflection attacks, an attacker spoofs your IP address and sends requests for information to your servers. These attacks amplify malicious attacks to generate more of them and obscure the source of the attack.⁹

Many people using this technique attack open domain name servers (DNS) to reroute requests from the server to the attacker. Because the data appears to be legitimate, it’s hard to prevent these types of attacks. The resulting downtime shuts legitimate users out of your system.

The internet of things (IoT) refers to internet-connected devices. As a business owner, you may use IoT sensors to collect valuable operational data. Or you might have a smart building with internet-controlled lighting and HVAC systems. IoT-based DoS attacks use these devices to disrupt your system.

An attacker can use a Mirai botnet to hijack your IoT devices and use them to launch DoS attacks.¹⁰ A Reaper botnet exploits known vulnerabilities to attack IoT devices and use them to launch attacks.

As networks continue to become more sophisticated, so too do DoS attacks. Some cybercriminals are using tools powered by artificial intelligence (AI) to find system vulnerabilities and even launch cyberattacks.¹¹ These systems can find information about your employees and use their networks to attack, which makes them harder to detect.¹¹

Cryptojacking is another emerging DoS attack category. This type of attack involves using your network to mine cryptocurrency. While the attackers are cryptomining, your system slows down for legitimate requests. Along with system downtime, a cryptojacking attack can also cause your hardware to overheat and increase your electricity costs.¹²

DoS attacks cost your company money. Service disruptions keep your customers from carrying out legitimate transactions with your business. Downtime can also erode customer confidence and damage your company’s reputation. It is important to know how to prevent DoS attacks to keep your network up and running.

Start by monitoring your system for slowdowns or inactivity on your website. Once you know how your system normally operates, you can detect anomalies. Prevent DoS attacks by working with internet service providers and other vendors that offer DoS protection.¹³ Make sure you and all other system administrators learn about DoS prevention. Routinely monitor and update networks so you can patch vulnerabilities.

Update your firewalls and install prevention systems on your network to detect and block fraudulent traffic. Add extra protection with anti-virus and anti-malware software. Finally, develop a restoration plan. Regularly back up your data and test your backups, so you can restore functionality if you are subject to a DoS attack.

DoS attacks are sophisticated efforts to make your network and your website unresponsive to legitimate traffic. When successful, these attacks keep your customers from doing business with you. They also expose your system’s vulnerabilities, which can damage your brand with customers.

The online Master of Science in Cybersecurity from Yeshiva University’s Katz School of Science and Health will prepare you to lead your company’s efforts to prevent DoS attacks. Our affordable program arms you with the skillsets to identify and prevent these attacks through real-world simulations and hands-on training. You will learn from industry experts with real experience to learn critical techniques for mitigating cyber threats.

Whether you’re interested in advancing your current career in cybersecurity or seeking a career change, this program offers everything you need to get started. Contact an admissions outreach advisor today to learn more.