What is Denial of Service (DoS)? - SentinelOne

What is Denial of Service (DoS)?

Introduction

Denial of Service (DoS) in computer security refers to an attack in which an attacker overwhelms a network or system with a high volume of traffic or requests, making it unavailable to legitimate users. This can be achieved through various methods, such as flooding a server with traffic from multiple sources (distributed denial of service or DDoS attack), exploiting vulnerabilities in software or hardware, or simply overwhelming the system with legitimate requests. The goal of a DoS attack is to disrupt the availability of the targeted network or system, making it unavailable to legitimate users and potentially causing damage or financial loss. To protect against DoS attacks, organizations can implement security controls, such as firewalls and intrusion detection and prevention systems, to block or filter traffic and detect and mitigate potential attacks.

What May Cause a Denial of Service (DoS)?

DoS attacks are performed by individuals or groups with different motivations and goals. Some attackers may be motivated by political or ideological reasons and use DoS attacks to express their views or disrupt the operations of a targeted organization. Other attackers may be motivated by financial gain and use DoS attacks to extort money from a targeted organization. In some cases, attackers may be motivated by personal grudges or revenge and use DoS attacks to retaliate against a targeted individual or organization. Overall, the motivations and origins of DoS attacks can be difficult to determine, as attackers often use sophisticated techniques to hide their identities and locations.

A denial of service (DoS) attack is caused by an attacker who sends a high volume of traffic or requests to a network or system, overwhelming it and making it unavailable to legitimate users. This can be achieved through a variety of methods, such as:

  1. Flooding a server with traffic from multiple sources (distributed denial of service or DDoS attack): In this attack, the attacker uses multiple systems to send traffic to the targeted server, overwhelming it and making it unavailable.
  2. Exploiting vulnerabilities in software or hardware: The attacker can exploit vulnerabilities in software or hardware to cause the targeted system to crash or become unavailable.
  3. Overwhelming the system with legitimate requests: The attacker can send a high volume of legitimate requests to the targeted system, overwhelming it and making it unavailable to legitimate users.

These attacks can be difficult to detect and prevent, as they may not necessarily involve malicious or unauthorized activity. However, they can cause significant disruption and damage to the targeted network or system and have serious financial and legal consequences for the organization.

What are the Types of Denial of Service (DoS) Attacks?

There are several common types of denial of service (DoS) attacks, including:

  1. Distributed denial of service (DDoS) attack: This type of attack involves sending a high volume of traffic from multiple sources to a targeted server, overwhelming it, and making it unavailable to legitimate users.
  2. Ping of death attack: This attack involves sending a ping packet larger than the maximum allowed size, causing the targeted system to crash or become unresponsive.
  3. Teardrop attack: This type involves sending packets with overlapping or fragmented data, which can cause the targeted system to crash or become unresponsive.
  4. SYN flood attack: This type of attack involves sending many SYN (synchronized) packets to a targeted system, which can cause it to become overwhelmed and unresponsive.
  5. Application-layer attack: This type of attack involves exploiting vulnerabilities in an application or service, such as a web server, to cause it to crash or become unresponsive.

These are just a few examples of the many types of DoS attacks that can be used to disrupt the availability of a network or system. To protect against these threats, organizations can implement security controls and practices, such as firewalls, intrusion detection and prevention systems, and regular updates and patches.

One of the most well-known denial of service (DoS) attacks is the distributed denial of service (DDoS) attack. In a DDoS attack, the attacker uses multiple systems, often called a botnet, to send a high volume of traffic to a targeted server, overwhelming it and making it unavailable to legitimate users. This type of attack can be difficult to detect and prevent, as it involves multiple systems and can appear to be legitimate traffic. In recent years, there have been several high-profile DDoS attacks, including the Mirai botnet attack in 2016, which targeted the Krebs on Security website and other major websites, and the attack on the Dyn DNS provider in 2016, which disrupted access to major websites such as Twitter and Netflix. To protect against DDoS attacks, organizations can use security controls, such as firewalls, intrusion detection and prevention systems, and specialized DDoS protection services.

What is the Difference Between DoS and DDoS Attacks?

The main difference between a denial of service (DoS) attack and a distributed denial of service (DDoS) attack is the number of systems involved. In a DoS attack, the attacker uses a single system to send high traffic or requests to a targeted network or system, overwhelming it and making it unavailable to legitimate users. In a DDoS attack, the attacker uses multiple systems, often called a botnet, to send a high volume of traffic or requests to the targeted network or system, overwhelming it and making it unavailable. This makes a DDoS attack more difficult to detect and prevent, as the traffic appears to be coming from multiple legitimate sources. To protect against both types of attacks, organizations can implement security controls, such as firewalls and intrusion detection and prevention systems, regularly update software and provide employee training on cybersecurity best practices.

A distributed denial of service (DDoS) attack is generally considered more dangerous than a denial of service (DoS) attack. This is because a DDoS attack involves multiple systems, often called a botnet, sending high traffic or requests to a targeted network or system. This makes it more difficult to detect and prevent, as the traffic appears to be coming from multiple legitimate sources. In addition, a DDoS attack can generate a much higher volume of traffic than a single system, making it more likely to overwhelm the targeted network or system and making it unavailable to legitimate users. To protect against both types of attacks, organizations can implement security controls, such as firewalls and intrusion detection and prevention systems, regularly update software and provide employee training on cybersecurity best practices.

How to Stay Safe from Denial of Service (DoS) attacks?

To stay safe from denial of service (DoS) attacks, organizations can implement the following security controls and practices:

  1. Firewalls and intrusion detection and prevention systems: These can be used to block or filter incoming traffic and to detect and prevent potential DoS attacks.
  2. Load balancers and content delivery networks (CDNs) can distribute incoming traffic across multiple servers, reducing the impact of a DoS attack on any single server.
  3. DDoS protection services: Organizations can use specialized services to monitor incoming traffic and block or filter malicious traffic before it reaches the targeted system.
  4. Regular updates and patches: Keeping software and operating systems up to date with the latest patches and updates can help to prevent attackers from exploiting known vulnerabilities.
  5. Employee training and awareness: Providing employees with training and awareness programs can help to educate them on the risks and consequences of DoS attacks, and how to identify and avoid potential threats.

By implementing these measures and regularly reviewing and updating them as needed, organizations can reduce their risk of being impacted by a DoS attack and maintain the availability of their systems and networks.