Table of Contents
Introduction
Both denial-of-service (DoS) attacks and (distributed-denial-of-service) DDoS attacks attempt to take a service offline by overwhelming it with traffic. And since there’s just one “D” that separates DoS and DDoS, you might expect they’d have a lot more common, but that’s where the similarities end.
Understanding the differences between DoS and DDoS attacks is important to ensure your organization is protected against the breadth of attacks that overwhelm online services to disrupt availability. In this blog, we’ll explore how DoS and DDoS attacks work, the key characteristics of each, and common types of attacks. We’ll also dig into the many differences and how to detect and mitigate the full breadth of these threats.
Understanding DoS Attacks
Think of a DoS attack as one-on-one combat with a threat actor. In a DoS attack, one online computer floods another online computer (usually a server) resulting in denial-of-service to legitimate users. The objective is to take a website offline so that it is no longer available to additional requests.
Most Common Types of DoS Attacks
DoS attacks typically fall into three categories.
Flood attacks take advantage of the source computer having access to more bandwidth than the receiving machine. The targeted server becomes saturated with an overwhelming number of packets that exceed its capacity, resulting in denial-of-service.
IP fragmentation attacks break down IP packets into small, incomplete fragments that the receiving computer cannot reassemble. The system becomes bogged down trying to reassemble the packets and network performance suffers and eventually cannot handle legitimate traffic.
Buffer overflow attacks take advantage of a software flaw to send an amount of data to a targeted system that exceeds the system’s buffer’s capacity. As the data overflows into other buffers, the machine’s hard disk space and memory are consumed, and performance becomes sluggish. Ultimately the machine crashes, resulting in denial-of-service.
Some of the most common types of DoS attacks include: Slowloris attacks, Ping flood attacks, Ping of Death (PoD) attacks, Teardrop attacks, and LOIC. It may be confusing to see these DoS attacks also described as DDoS attacks, but both are true. DoS attacks can be executed as DDoS attacks to maximize the impact. In the next section we explain how.
Understanding DDoS Attacks
Think of a DDoS attack as going up against an army of soldiers with the threat actor as the general. Cybercriminals who carry out DDoS attacks use networks of internet-connected devices (computers, routers, or IoT devices) that they have infected with malware so that they can control each device remotely. These infected devices are known as bots (or zombies), and a group of bots forms a botnet.
Once they’ve established a botnet, the attackers can direct an attack by sending remote instructions to each bot. Each bot sends requests to the target’s IP address, causing the server or network to become overwhelmed and resulting in a denial-of-service to normal traffic. These can be the same tasks a DoS attack would execute but on a grander scale, or a combination of more complex actions and additional vectors with even more damaging consequences for victims. Either way, the magnitude of a DDoS attack far exceeds that of a DoS attack, so it is not surprising that DDoS attacks are far more prevalent than DoS attacks.
The Most Common Types of DDoS Attacks
There are various types of DDoS attacks, and they are constantly evolving as technology evolves. Currently, DDoS attacks fall into three main categories.
Volumetric attacks exploit bandwidth resources by using a botnet to send a high volume of request packets to the network. The network becomes overwhelmed with requests which causes services to slow down and even stop entirely. Common types including SYN flood attacks, ICMP flood attacks, and UDP flood attacks.
Protocol attacks exploit weaknesses in Layers 3 and 4 of the OSI model, such as weaknesses in the TCP protocol. By sending requests and either not answering as expected or sending another request, the network slows down and eventually crashes. SYN/ACK flood attacks, ACK flood attacks, and TCP connection exhaustion attacks are a few examples.
Application layer attacks, also known as Layer 7 attacks, exploit vulnerabilities in web applications and services and in APIs to cause a shutdown. Examples include HTTP/HTTPS flood attacks and Slowloris attacks.
Threat actors also incorporate additional techniques to make these attacks more difficult to defend against. For example:
- Reflection is used to obscure the source of the attack traffic by spoofing IP addresses so that the responses to requests go to the targeted victim.
- Amplification magnifies the amount of malicious traffic the attacker can generate by taking advantage of a protocol flaw where small requests can lead to much larger responses.
- Spoofing uses falsified source IP addresses to send packets, overwhelming the target’s infrastructure and making it challenging to trace the origin of the attack.
- Ransom DDoS attacks add another layer of leverage because the attacker sets up or even launches a DDoS attack and then demands money in exchange for not carrying it out or for stopping it.
Key Characteristics and Differences Between DoS and DDoS Attacks
At their core, DoS attacks and DDoS attacks have the same goal: to take a service offline by overwhelming it with traffic. But the way they go about achieving this goal makes these attacks very different from each other.
| Characteristic | DoS | DDoS |
|---|---|---|
|
Source |
Single source/system targets the victim’s system |
Multiple sources/systems (often as a botnet) attack the victim’s system |
|
Complexity |
Low |
|
|
Volume of Traffic |
Traffic volume is high, but since it originates from only one source it is inherently limited |
Traffic is often volumetric due to the number of sources used. However, lower traffic volumes are increasingly being used to evade detection while still disrupting availability and performance |
|
Speed of attack |
Slower because it is only executed from a single source |
Fast due to the number of systems involved, but sometimes DDoS attacks can be slow when being used for reconnaissance |
|
Traceability |
Relatively easy since it originates from a single source, although the use of a spoofed IP address makes traceability more difficult |
Difficult since attackers use multiple devices (botnets) to send packets from multiple locations |
|
Detection and Mitigation |
Relatively easy to block since it comes from a single source |
Difficult to block without advanced DDoS protection since multiple devices are sending packets and attacking from multiple locations |
|
Duration |
Hours or days |
Days, weeks or longer |
|
Impact |
Denial of service/disruption |
Denial of service/disruption, hacktivism, cyber warfare, extortion, competitive advantage |
Widening Gap Between DoS and DDoS Attacks
As DDoS attacks continue to evolve, DoS attacks have become less prevalent. Our 2025 Threat Intelligence Report confirms that through the use of automation and affordable tools like DDoS-as-a-service and botnets for hire, threat actors with limited technical knowledge can execute DDoS attacks. Additionally, DDoS attacks have become more difficult to detect and more destructive as they are increasingly being used as a strategic tool to:
- Probe for weaknesses attackers can use to launch other types of attacks like data breaches
- Test for mitigation thresholds
- Distract security teams from more targeted activities like ransomware attacks
Ultimately, the impact of a DDoS attack on an organization can include not just the cost of downtime and lost revenue, but also operational costs to mitigate and deal with the aftermath of an attack, reputational damage, paying a ransom, and regulatory penalties.
How to Protect Against DoS and DDoS Attacks
As with all threats, an ounce of prevention is worth a pound of cure. To defend against DoS and DDoS attacks, organizations should use a combination of best practices and technology.
Employee Education
Educate employees on the dangers of DDoS attacks and how to avoid becoming infected by using strong passwords, multi-factor authentication, and not clicking on suspicious links or attachments in emails from unknown sources.
Traffic Monitoring and Rate Limiting
Implement robust traffic monitoring and anomaly detection systems. By establishing a baseline of normal traffic behavior, you can quickly identify any deviations or anomalies to mitigate an attack.
Set up rate limiting on your network devices to restrict the number of requests from a single source within a specified timeframe. This can help prevent overwhelming your servers with excessive traffic.
IP Blocklists
Maintain a list of known malicious IP addresses and use IP blocklists to block traffic from these sources. Conversely, consider IP allow lists to only allow traffic from trusted sources.
Network Redundancy and Failover Plans
Use load balancers and failover mechanisms that distribute traffic across different servers and cloud resources to help mitigate the impact of an attack and assist with continuity of service while IT teams investigate and respond. Additionally, leverage Content Delivery Networks (CDNs) to distribute your website’s content across multiple servers and locations. CDNs can absorb and distribute traffic, minimizing the impact of DDoS attacks on a single server.
Cloud-based Services
Consider migrating your services to cloud-based platforms that offer scalable infrastructure. Cloud providers often have DDoS protection mechanisms in place and can absorb large volumes of traffic. A hybrid setup – where you have cloud-based back-up of on-premises protection service– is another option.
Regularly Update and Patch Systems
This is of course a general IT best practice, but DDoS attackers often exploit vulnerabilities in outdated software, so staying current is crucial. Be sure to regularly update and patch all systems and software.
Secure IoT Devices
Secure IoT devices by deploying security features whenever possible. Additionally, validate your inventory of IoT devices and make sure they are up to date with patches, apply network segmentation to limit movement of traffic from IoT devices to other parts of the network, and use endpoint detection/protection tools if the IoT device has the compute power to run the software required.
Invest in Advanced DDoS Protection
A proven DDoS protection solution will mitigate the gamut of denial of service attacks and ensure you stay ahead of emerging threats. The most effective solutions will allow you to maintain uninterrupted service availability even in the midst of a DDoS attack. When coupled with real-time threat intelligence, these solutions can also protect you against follow-on malicious activity including data leakage, ransomware attacks, and other threats to your operations.
Conclusion
DoS and DDoS attacks both attempt to take a service offline by overwhelming it with traffic. On the surface they seem similar, but when you dig a little deeper the differences are dramatic. Because DDoS attacks enlist an army of internet-connected devices that have been infected with malware to execute the attack, the speed, complexity, volume, and impact of DDoS attacks are orders of magnitude greater than DoS attacks.
There are several best practices and technologies to mitigate and prevent DoS and DDoS attacks, including practical tips like employee education, updating systems and software, traffic monitoring, rate limiting, IP blocklists, network redundancy and failovers, and moving to cloud-based services with DDoS protection mechanisms in place.
However, the most effective way to protect against a gamut of denial-of-service attacks is by implementing an advanced DDoS protection solution. DDoS protection coupled with intelligence to stay ahead of emerging and evolving threats, provides uninterrupted service availability even in the midst of a DDoS attack. Comprehensive DDoS protection can also defend against follow-on malicious activity including data leakage, ransomware attacks, and other threats to your operations. Visit our threat intelligence research center for more information on DDoS defense in depth.
FAQ
In a DoS attack, one online computer floods another online computer (usually a server) resulting in denial-of-service to legitimate users. The objective is to take a website offline so that it is no longer available to additional requests.
DDoS attacks use networks of internet-connected devices (computers, routers, or IoT devices) that they have infected with malware so that they can control each device remotely. These infected devices are known as bots (or zombies), and a group of bots forms a botnet.
Once they’ve established a botnet, the attackers can direct an attack by sending remote instructions to each bot. Each bot sends requests to the target’s IP address, causing the server or network to become overwhelmed and resulting in a denial-of-service to normal traffic.
DoS attacks typically fall into three categories: Flood attacks, IP fragmentation attacks, and buffer overflow attacks. Some of the most common types of attacks include: Slowloris attacks, Ping flood attacks, Ping of Death (PoD) attacks, Teardrop attacks, and LOIC. These DoS attacks can also be executed as DDoS attacks to maximize impact.
DDoS attacks fall into three main categories: Volumetric attacks, Protocol attacks, and Application layer attacks. Threat actors incorporate additional techniques to make these attacks even more difficult to defend against including reflection and amplification, spoofing, and ransomware. Some common types of DDoS attacks include: SNY flood attacks, ICMP flood attacks, UDP flood attacks, ACK flood attacks, and Slowloris attacks.
Organizations can use best practices and technologies to protect their organization from DoS and DDoS attacks, including employee education, updating systems and software, traffic monitoring, rate limiting, IP blocklists, network redundancy and failovers, and moving to cloud-based services with DDoS protection mechanisms in place.
Threat actors continue to use DoS attacks to disrupt service availability. However, because the impact of a DDoS attack far exceeds that of a DoS attack, it is not surprising that DDoS attacks are far more prevalent today.
Yes. Purpose-built advanced DDoS protection coupled with intelligence helps organizations stay ahead of emerging and evolving threats, and provides uninterrupted service availability even in the midst of a DDoS attack. Comprehensive DDoS protection can also defend against follow-on malicious activity including data leakage, ransomware attacks, and other threats to your operations.
