What Is a Denial-of-Service (DoS) Attack?

A Denial-of-Service (DoS) attack is a cyber assault aimed at overwhelming a system, server, or network, rendering it unavailable to users. Attackers flood the target with an excessive amount of traffic or send information that triggers a crash, preventing legitimate users from accessing services.

DoS attacks can be launched using a single device, making them easier to execute but still disruptive. They exploit vulnerabilities in network infrastructure or software to overload resources.

While not intended to steal data, DoS attacks cause significant downtime, leading to loss of productivity and potential financial damage. Protecting against such attacks requires robust security measures, including firewalls, traffic monitoring, and intrusion detection systems.

Watch the video below to learn a denial service attack example.

The Impact of DoS Attacks on Businesses

A DoS attack can have a devastating impact on businesses by interrupting operations and causing financial and reputational damage. Understanding the key effects of these attacks is essential for businesses to protect themselves and maintain continuity. Here are the main ways DoS attacks affect businesses:

• Service disruption: DoS attacks cause downtime, stopping businesses from delivering their services.
• Revenue loss: Companies that rely on online operations can lose significant income during this downtime.
• Reputation damage: Frustrated customers who can’t access services may lose trust, harming the company’s image.
• Additional costs: Businesses often face extra expenses to resolve the attack and restore services.
• Customer trust: Prolonged disruptions can weaken customer loyalty and long-term relationships.
• Need for protection: To prevent these problems, businesses need strong defenses against DoS attacks to ensure smooth operations and protect their reputation.

How Do DoS Attacks Work?

A DoS attack (Denial of Service) works by flooding a system, server, or network with too much traffic, causing it to slow down or crash, making it unavailable to real users. Attackers send more requests than the system can handle, consuming its resources and blocking legitimate access.

This can be done with a single device or through a botnet, a group of compromised devices used in DDoS attacks (Distributed Denial of Service).

The goal is to overwhelm the system and make it unresponsive, which is a common example of a DoS attack. DoS attacks and DDoS service attacks exploit vulnerabilities in a system's software or network to cause these disruptions.

Watch the video below to learn how ddos service attacks work.

To protect against them, businesses should use DDoS protection tools like firewalls and traffic filters to prevent harmful requests and keep services running smoothly.

Types of Denial-of-Service (DoS) Attacks

Types of Denial-of-Service (DoS) Attacks are designed to overwhelm systems in different ways, causing service disruptions.

Buffer Overflow Attacks overload a system’s memory, while Flood Attacks send massive amounts of traffic to overwhelm networks. Application Layer Attacks focus on disrupting specific software functions, and Protocol Attacks exploit weaknesses in network protocols. Volumetric Attacks consume large amounts of bandwidth, and Cloud-Based Attacks use the scale of cloud services to amplify the attack.

In the next sections, we’ll break down each type to understand their specific effects on systems.

Buffer Overflow Attacks

Buffer Overflow Attacks happen when a system gets more data than it can handle, causing it to crash or act unpredictably.

The specific danger of this attack is that the excess data overflows into other parts of the system’s memory, potentially allowing attackers to insert malicious code or take control of the system.

It’s a common way to disrupt services or gain access to sensitive information. Once the system is compromised, attackers can execute malicious actions, such as stealing data or disabling critical functions.

These vulnerabilities usually come from outdated or poorly designed software. To prevent this, businesses should regularly update their software and use techniques like input validation to block these types of attacks.

Flood Attacks

Flood Attacks overwhelm a system by sending an excessive amount of traffic or requests, far more than the system can handle. The goal is to exhaust the system’s resources, making it slow or completely unresponsive to legitimate users.

These attacks can target various parts of a network, such as servers, routers, or bandwidth. Unlike other attacks that exploit specific vulnerabilities, flood attacks rely on large amounts of traffic to disrupt services. They are often used in DoS and DDoS attacks, where either one device or many devices (botnets) generate the traffic. This method disrupts normal operations and can cause significant downtime.

To defend against flood attacks, businesses use firewalls, traffic filtering, and rate-limiting tools to manage incoming traffic.

Application Layer Attacks

Application Layer Attacks target specific software applications rather than the entire network. These attacks focus on disrupting the functions of web applications by sending seemingly legitimate requests that overwhelm the server. Unlike other attacks that target network bandwidth, application layer attacks consume server resources like CPU and memory, making the application slow or unavailable to real users. This type of attack is difficult to detect because the traffic appears normal but is designed to exhaust the application. DoS and DDoS attacks often use this method to bring down high-profile websites or services.

Businesses can protect against these attacks by implementing web application firewalls (WAFs) and closely monitoring traffic for unusual patterns.

Protocol Attacks

Protocol Attacks exploit weaknesses in communication protocols, such as TCP/IP, to overwhelm a system or network. These attacks target the processes that handle data exchange, disrupting connections and making services unavailable to legitimate users. Examples include SYN floods and ping of death attacks, which overload servers by manipulating how protocols manage requests. Protocol attacks can cause significant damage because they consume server resources, such as bandwidth or memory, without requiring a large amount of traffic.

Organizations can defend against these attacks by implementing firewalls, using intrusion detection systems, and applying rate-limiting techniques to regulate protocol traffic.

Volumetric Attacks

Volumetric Attacks aim to overwhelm a network’s bandwidth by flooding it with a massive amount of data, making services slow or completely inaccessible. Attackers use techniques such as UDP floods or DNS amplification to generate large volumes of traffic that saturate the network. The goal is to consume all available bandwidth, preventing legitimate users from accessing the system. These attacks don’t exploit specific vulnerabilities but rely on sheer volume to disrupt operations.

To protect against volumetric attacks, organizations can implement traffic filtering, use content delivery networks (CDNs), and deploy scalable bandwidth solutions to handle large volumes of traffic.

Cloud-Based Attacks

Cloud-Based Attacks leverage the scalability of cloud infrastructure to amplify the impact of a Denial-of-Service (DoS) attack. Attackers use compromised cloud resources to generate massive amounts of traffic, overwhelming the target system or network. These attacks are especially dangerous because cloud platforms can easily scale, making the attack larger and more difficult to stop. Cloud-based attacks can target both cloud services and traditional on-premises systems.

To defend against these attacks, businesses should implement strong cloud security practices, including traffic monitoring, rate-limiting, and collaborating with cloud providers to mitigate threats at the infrastructure level.

Watch the video below for examples of both DoS and DDoS attacks, with a detailed explanation of their types.

What Are the Main Differences Between DoS and DDoS Attacks?

The main difference between DoS and DDoS attacks lies in how they are carried out and their impact. A DoS attack (Denial of Service) is launched from a single device, flooding the target system with traffic to overwhelm it.

It’s like one person repeatedly knocking on your door, making it hard for anyone else to get in. On the other hand, a DDoS attack (Distributed Denial of Service) uses many devices, often part of a botnet, to send traffic from different locations all at once.

This is more like hundreds or thousands of people trying to knock on your door at the same time, making it nearly impossible to stop.

DDoS attacks are much more difficult to defend against because the traffic comes from many sources, making it harder to block. Both attacks aim to disrupt services, but DDoS attacks are more powerful and require stronger DDoS protection to prevent widespread damage.

What Are the Common Techniques Used in DoS Attacks?

Denial of Service (DoS) and Distributed Denial of Service (DDoS) attacks are methods used by attackers to overwhelm a network or system, making it unavailable to legitimate users. Here are the common techniques used in these attacks:

1. Traffic Flooding: Attackers flood the target with massive amounts of traffic, consuming all available bandwidth or resources. In a DoS attack, this is done from a single source, while in a DDoS attack, multiple devices (often compromised) send traffic to overload the system.
2. SYN Floods: This involves sending a large number of incomplete connection requests to a server, causing it to use up resources and eventually crash or become unresponsive.
3. Ping of Death: Attackers send oversized or malformed packets that a system cannot handle, causing it to crash.
4. Application Layer Attacks: These attacks focus on specific applications, such as sending slow or incomplete requests that overload the application, making it unavailable.
5. Botnets in DDoS: A DDoS attack amplifies the effects by using a botnet, a network of compromised devices, to send traffic from multiple sources, making it harder to defend against.

Preventing DDoS attacks involves using DDoS protection solutions that can filter malicious traffic, distribute load effectively, and detect attacks early to mitigate the impact.

Watch the Youtube video below and see how a real time DDos attack showcase.

How to Identify If a DoS Attack Has Occured?

To identify if a DoS attack or DDoS attack has occurred, there are some clear signs to watch for. The most common sign is your website or service suddenly becoming slow or unavailable for no obvious reason.

You might also see a big surge in traffic, especially from many different locations or IP addresses, which can overload your server. Repeated server crashes or a lot of incomplete connection requests (like SYN floods) are also warning signs.

You may notice that key resources like your CPU (Central Processing Unit, or the “brain” of your system), memory, or bandwidth are being maxed out. Monitoring tools can help spot these unusual traffic patterns, which are typical of a denial of service attack.

Using DDoS protection can help detect these attacks early and block harmful traffic before it causes too much damage.

How to Prevent Denial-of-Service (DoS) Attacks?

Preventing DoS attacks requires proactive steps to safeguard systems and minimize disruptions. With the right tools and strategies, businesses can significantly reduce the risk of an attack causing downtime or financial loss. Here’s how to prevent Denial-of-Service (DoS) attacks:

• Use firewalls and intrusion detection systems: These tools monitor and filter out suspicious traffic before it reaches your servers.
• Deploy a content delivery network (CDN) or load balancer: These distribute incoming traffic to reduce the risk of overload.
• Regularly update software: Keep all systems and software up-to-date to close off security gaps that attackers might exploit.
• Implement DDoS protection services: These detect and block large-scale attacks before serious damage occurs. Examples include Cloudflare, AWS Shield, and Akamai Kona Site Defender, offering advanced threat detection, traffic filtering, and mitigation tools to prevent systems from being overwhelmed.
• Create a response plan: Having a strategy in place ensures quick action to minimize the effects of an attack and restore services.

Alternatively, watch the video about ddos attacks how to prevent them.

Strengthen Your Protection Against DoS Attacks with Keepnet

Keepnet’s security awareness training offers a comprehensive approach to equipping your employees with the knowledge and skills needed to prevent, identify, and respond to DoS and DDoS attacks effectively.

Our training programs are designed not only to educate staff about the technical aspects of such attacks but also to raise awareness about the social engineering tactics often used to initiate them. By combining technical know-how with an understanding of human factors, your organization can develop a well-rounded defense strategy.

By fostering a culture of cybersecurity awareness, Keepnet helps your organization build resilience not just against DoS attacks but also against the broader spectrum of social engineering and cyber threats.