DDoS vs DoS | Difference Between DoS and DDoS Attacks

Cybersecurity threats come in many forms, and among the most disruptive are DoS (Denial-of-Service) and DDoS (Distributed Denial-of-Service) attacks. While they may seem similar, the scale, method, and impact of DoS and DDoS attacks differ significantly. 

This article explores each attack type, its features, examples, and lists out the key differences between DoS and DDoS attacks in cyber security.

Furthermore, if you are interested in learning the practical methods of preventing these attacks, you can check out our Cyber security courses.

What is a DoS attack? 

Denial-of-Service attacks are deliberate attempts to make online services slow, unreliable, or entirely inaccessible by flooding them with malicious traffic. These attacks can target websites, email servers, APIs, and even entire networks.  

A DoS attack is launched from a single source or device, which sends an overwhelming amount of traffic or requests to a target system. The goal is to consume system resources, such as CPU, memory, or bandwidth, until the target becomes unresponsive or crashes. 

Characteristics of DoS Attacks 

Some unique characteristics of Denial of Service attacks are: 

● Launched from one machine or IP address. 

● Aims to exhaust system resources like CPU, RAM, bandwidth, or storage. 

● Often causes service slowdown or complete unavailability. 

● Focuses on disruption, not stealing or altering data. 

● High traffic spikes from a single IP make it easier to trace than DDoS attacks.

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What is a DDoS Attack? 

A Distributed Denial of Service (DDoS) attack is an unauthorized attempt to disrupt a targeted server, service, or network's normal operation by flooding it with a large volume of traffic from multiple sources. These sources are frequently compromised on PCs, Internet of Things gadgets, or bots that are part of a network called a botnet. 

It becomes very challenging to block fraudulent traffic without hurting genuine users because the attack occurs from multiple sites at the same time. They frequently target networks or websites to disrupt, extort, or harm their reputation. 

Characteristic of DDoS Attacks 

The following are the characteristics: 

●  DDoS attacks can target websites, online services, or entire networks, making them versatile in their impact. 

●  The scale of traffic generated during a DDoS attack can be massive, sometimes reaching hundreds of gigabits per second. 

●  Attackers may use different attack vectors simultaneously, such as volumetric attacks, protocol attacks, and application-layer attacks, to bypass defenses. 

●  DDoS attacks can be motivated by financial gain, political agendas, or as a smokescreen for other malicious activities. 

Key Differences Between DoS and DDoS 

Here’s a table showing the key differences between DoS and DDoS attacks: 

Types of DoS and DDoS Attacks

DoS and DDoS attacks can vary significantly in their forms and targets. While some attacks may be minor, causing temporary disruptions, others can be severe enough to completely halt a service. Below is a list of common types of DoS and DDoS attacks:

1. Volumetric Attacks

These attacks aim to consume all available bandwidth between the target and the Internet.

Example: UDP Flood, in which attackers send massive amounts of User Datagram Protocol (UDP) packets to random ports on the victim's system, overwhelming the network.

2. Protocol Attacks (State-Exhaustion Attacks)

These attacks exploit weaknesses in protocols like TCP, DNS, and others by consuming resources of servers, firewalls, and load balancers.

Example: SYN Flood, in which the attacker sends numerous TCP SYN packets to initiate a connection but never completes the handshake, exhausting server resources.

3. Application Layer Attacks (Layer 7 Attacks)

These attacks target specific application functions by sending seemingly legitimate and well-formed requests that overwhelm the application.

Example: HTTP Flood, in which the Attackers send a flood of HTTP GET or POST requests to a website, overwhelming the server.

4. DNS Amplification

This is a reflection-based volumetric attack where small queries generate large responses.

Example: A 60-byte DNS query can generate a 4,000-byte response, allowing attackers to flood the target with high bandwidth traffic.

5. NTP Amplification

This attack abuses the Network Time Protocol (NTP), particularly the monlist command, which returns a list of the last 600 IP addresses that requested time from the server.

Example: Attackers send a small forged NTP request to multiple NTP servers, and each sends a large response to the victim, amplifying the attack’s scale.

6. Slowloris Attack

Slowloris keeps many connections to the target web server open and holds them open as long as possible by sending partial HTTP requests.

Example: The attacker sends incomplete HTTP headers at regular intervals, preventing the server from closing the connections and eventually exhausting its connection pool.

What is More Dangerous Between DDoS and DoS Attacks? 

DDoS (Distributed Denial of Service) attacks are generally more dangerous and impactful than DoS (Denial of Service) attacks due to their scale, complexity, and difficulty to mitigate. 

Here's Why: 

● DDoS attacks come from many compromised devices (called a botnet), making it much harder to trace and block the malicious traffic compared to a single-source DoS attack. 

● DDoS attacks can generate enormous traffic volumes, often enough to bring down even large, well-protected networks or websites. DoS attacks usually involve less traffic and are easier to contain. 

● DDoS attacks often use multiple attack vectors at once (e.g., volumetric, protocol, and application-layer attacks), making defense more complex. DoS attacks are usually simpler. 

● Since DDoS traffic is distributed across many devices and IPs, it blends in with normal traffic and can bypass basic security controls. DoS traffic is easier to spot and block. 

● DDoS attacks can cause prolonged service outages, lead to financial losses, damage reputation, and even data breaches in some cases. DoS attacks are usually short-lived and localized. 

How to Prevent DoS and DDos Attacks?

Combating DoS and DDoS attacks requires a multi-layered security strategy: 

Conclusion 

While both DoS and DDoS attacks aim to disrupt services, they differ greatly in their execution and impact. DoS attacks are simpler and easier to control, while DDoS attacks are more complex and damaging. Understanding these differences is crucial for network administrators and cybersecurity professionals to build resilient defenses and respond effectively when under attack. 

Proactive planning, real-time monitoring, and adopting strong mitigation tools are the best defenses against these disruptive threats.