10 Different Types of DDoS Attacks and How to Prevent Them

Hey there! DDoS attacks are a major pain point for anyone running an online business or service these days. As networks and bots become more sophisticated, these distributed denial of service attacks are only growing in disruptiveness.

In this guide, I‘ll provide an in-depth look at 10 of the most common DDoS attack types, explain how each one can wreak havoc, and offer best practices to help keep these threats from shutting down your websites and services. I‘ve packed this article with stats, examples, insights and prevention tips I‘ve learned through my years as an IT security analyst.

My goal is to help you understand these attacks on a technical level and identify smart ways to defend against them. The more you know about the DDoS landscape, the better you can protect your organization and customers from outages and disruption. Let‘s get started!

What Exactly is a DDoS Attack?

Before diving into specific varieties, it helps to level set on what precisely a DDoS attack is.

A distributed denial of service attack refers to intentionally overwhelming an online service with traffic from multiple sources. By leveraging hundreds or thousands of internet-connected devices infected with malware, attackers can direct a flood of junk requests at a target website or server.

This massive volume of bogus traffic overloads infrastructure and prevents legitimate users from accessing the target during an attack. Just a fraction of the total traffic hitting the target is real human visitors – most is garbage from compromised botnet nodes.

According to recent stats from Kaspersky, 87% of organizations faced DDoS attacks in 2025. Attacks exceeded 1 Tbps in 13% of incidents! As these threats become more pervasive, it‘s essential to grasp the different flavors of DDoS and key protection strategies.

Next, let‘s examine the most widespread DDoS attack types witnessed in the wild today.

Major Categories of DDoS Attacks

Broadly speaking, DDoS attacks can be grouped into three categories based on the component of infrastructure targeted:

• Application Layer Attacks – Target websites, web servers and applications directly
• Protocol Attacks – Exploit communication protocols like TCP and UDP
• Volumetric Attacks – Attempt to overwhelm network capacity and bandwidth

Additionally, each category contains numerous specific attack types. Let‘s break down key methods under each category and how they threaten online services.

Application Layer Attacks

Application layer DDoS attacks are focused directly on crashing websites, disabling web servers and disrupting supporting applications. They achieve this by consuming application resources or manipulating application logic and data processes.

Some of the most common application layer attacks include:

HTTP Flood

An HTTP flood is one of the simplest yet most disruptive DDoS techniques. The attacker directs a tsunami of HTTP requests towards one or more web servers or applications.

Each HTTP request on its own is perfectly valid – but the sheer volume of requests rapidly overwhelms server resources. HTTP flooding attacks often seek to consume all available RAM, CPU and concurrent connection capacity on a web server.

With bandwidth so cheaply available via botnets, massive HTTP flooding attacks are easy to launch. According to Cloudflare, HTTP flooding makes up over 70% of all DDoS attacks. A major HTTP DDoS can choke out your website in the blink of an eye.

Slowloris

The Slowloris attack works by slowly sending partial HTTP requests to a web server. It opens multiple connections but keeps them open as long as possible by minimizing data transfer.

This gradually exhausts server resources as more connections remain open. Slowloris is difficult to detect because each request seems harmless on its own. The attack only requires minimal bandwidth but ties up web server capacity.

A single computer can take down major sites using Slowloris if protections aren‘t in place. High profile companies like Goldman Sachs, Bank of America, the FBI and others have fallen prey to Slowloris attacks.

SSL Attacks

Secure socket layer (SSL) attacks inundate HTTPS websites and apps with bogus requests for encrypted connections. Significant processing is required on the server side to handle SSL negotiations and encryption.

Floods of SSL connection requests can rapidly max out CPU usage, memory and concurrent connection limits – crashing unsecured HTTPS apps and sites. SSL attacks have increased over 600% year-over-year per Cloudflare data.

SQL Injection Attacks

SQL injection attacks exploit vulnerabilities in server-side web applications to compromise and disrupt databases. The attacker sends malicious SQL code in inputs like login forms, search boxes or URL parameters.

If sanitization isn‘t implemented properly, the injected SQL executes with the application‘s database privileges. This permits data theft, corruption, deletion and more.

Research shows SQL injection was linked to over 65% of data breaches – its risks go far beyond DDoS. Attackers can often leverage SQLi to fully takeover sites and servers in addition to causing denial of service.

Cross-Site Scripting (XSS)

A cross-site scripting vulnerability allows attackers to inject malicious JavaScript code into a vulnerable web page. When normal users visit the impacted page, the script executes inside their browser and can be leveraged for various attacks.

XSS is often used for session hijacking, phishing, inducing users to install malware and more. XSS can also be harnessed for DDoS by forcing multitudes of visiting browsers to flood a targeted site with requests.

Over two-thirds of websites are estimated to be vulnerable to XSS presently. The prevalence of XSS underscores the importance of robust input validation and output encoding in web apps.

DNS Flood

A DNS flood aims to overwhelm DNS servers by sending a tsunami of DNS lookup requests to disrupt services. DNS is a foundational internet protocol enabling human-readable domain names to be translated into machine-readable IP addresses by DNS servers.

By flooding core DNS servers with junk requests, attackers prevent legitimate domain name lookups from being handled properly. This indirectly disrupts access to websites, apps and web services that rely on DNS.

According to recent metrics, DNS amplification DDoS attacks have grown over 200% year-over-year. We‘ll discuss amplification attacks more below.

Protocol Attacks

Whereas application attacks target specific services and apps, protocol attacks operate at the network and transport layers. Protocol attacks seek to consume available bandwidth and overwhelm network infrastructure itself.

Some major examples include:

SYN Flood

A SYN flood leverages weaknesses in the TCP three-way handshake process to overwhelm victims. TCP connections begin with a SYN packet from the client to the server over a chosen port.

The server responds with a SYN-ACK over that port, and then the client sends an ACK to complete the handshake. The server keeps the half-open connection pending that final ACK.

SYN flood attacks send repeated SYN requests but never respond to the SYN-ACKs. Servers queue up connections waiting for ACKs that aren‘t coming. Soon all available sockets fill up, making it impossible to open legitimate connections.

UDP Flood

A UDP flood aims to saturate available bandwidth by flooding a target with User Datagram Protocol (UDP) packets. Because UDP is connectionless, packets can be sent rapidly without completing a handshake first.

With enough UDP traffic generated, networks become jammed and denial of service ensues. The lack of built-in validation for UDP packets makes floods harder to block based on anomalies. Recent stats show the prevalence of UDP flooding growing.

ICMP Flood

An ICMP flood exploits weaknesses in the Internet Control Message Protocol, used for communicating errors and network stats between endpoints.

By overwhelming networks and servers with ICMP echo requests (pings) and error packets, attackers consume available bandwidth and resources. It‘s similar to a UDP flood but uses ICMP specifically.

Smurf Attack

A smurf attack leverages spoofing and broadcasting to amplify DDoS traffic. First the attacker spoofs the victim‘s IP address as the source IP in an ICMP echo request sent to a network‘s broadcast address.

This broadcast address ensures all devices on that network receive the request – and all reply to the spoofed (victim‘s) IP. By layering amplification, smurf attacks can choke systems and networks with ease.

Volumetric Attacks

The end goal of volumetric DDoS attacks is simply to saturate available bandwidth with junk traffic. Volumetric attacks don‘t necessarily crash systems themselves but rather clog networks to cut off access.

Some prominent examples include:

DNS Amplification

DNS amplification attacks leverage DNS functionality to overwhelm targeted organizations via DDoS. The attacker sends large numbers of DNS queries to open DNS resolvers with the source IP address spoofed to be the victim‘s system.

When the DNS servers send their responses, they flood the victim‘s network with significantly more traffic than the requests generated. By amplifying traffic volume drastically through DNS, these attacks can cripple networks.

NTP Amplification

An NTP amplification attack exploits Network Time Protocol servers in similar fashion to DNS amplification. By spoofing requests to public NTP servers, the attacker directs expansive response traffic toward the victim network or server.

NTP responses are generally much larger than their requests – providing fertile ground for overwhelming DDoS attacks. Massive bandwidth can be leveraged via NTP reflection.

Chargen Amplification

Chargen amplification attacks take advantage of misconfigured network devices running the character generation (chargen) protocol. Chargen is meant to respond with a stream of characters for testing purposes.

By spoofing chargen requests to broadcast addresses, attackers amplify and direct huge responses toward victims as DDoS traffic. Chargen attacks exceeding 75Gbps have been reported recently.

How Can You Protect Against DDoS Attacks?

Now that you understand the most common DDoS threats, let‘s explore key prevention and mitigation strategies to help safeguard your online assets.

• Use DDoS mitigation services – Reputable cloud scrubbing services can identify attack traffic and block it before it saturates your network. This takes the burden off your infrastructure. Top providers like Cloudflare, Akamai and Radware offer DDoS mitigation.

• Enable rate limiting – Configure rate limiting on routers, firewalls, load balancers and other network gear to prevent traffic from exceeding capacity during attacks. Rate limiting helps maintain stability.

• Perform stress testing – Test your apps and infrastructure resilience via stress testing and load simulation. This reveals pain points to address and models real attacks. Some vendors offer live DDoS testing which is ideal.

• Have an emergency response plan – Define a documented DDoS response plan so your team is ready to detect and react to attacks. Include technical details, communication protocols, leadership contacts and reporting procedures.

• Follow secure coding best practices – Adhere to OWASP guidelines covering input validation, sanitization, error handling and other application security fundamentals. Perform rigorous code reviews and penetration testing.

• Require encryption – Mandate TLS 1.2+ and enable HTTP Strict Transport Security to prevent certain SSL attacks. Never allow unencrypted web connections.

• Monitor closely – Implement network monitoring to watch for unusual spikes in traffic, latency and other indicators of DDoS activity. Monitor actively rather than waiting for customers to complain.

• Harden infrastructure – Update network devices, OSes and application frameworks regularly. Limit unnecessary open ports and services. Disable unused protocols and IP addresses to minimize attack surface.

• Maintain backups – Keep recent backups of websites, databases, applications and other assets so you can rapidly restore services if attacks succeed. Test restores periodically.

Conclusion and Key Takeaways

I hope this guide provided useful insights into the most common DDoS attack types and key principles to protect your organization from these threats. Some key takeaways in review:

• Major categories of DDoS attacks include application layer, protocol and volumetric – each with distinct targets and methods.

• Leading attacks like HTTP flooding, SSL attacks, DNS amplification, Slowloris, SQLi and others can severely disrupt websites and networks.

• Core protections require using layered defenses like DDoS mitigation services, strong application security, encryption, monitoring and more.

With attacks rising in frequency, duration and complexity, it‘s crucial to understand the modern DDoS landscape and utilize robust safeguards. No single tool or tactic can eliminate risk entirely, but the right blend of measures will go a long way.

Hopefully this guide gave you some new insight into these threats, and whet your appetite for learning more about protecting your online presence! Let me know if you have any other DDoS topics you want me to cover in the future. Stay safe!