What is a Distributed Denial of Service (DDoS) Attack?

A Distributed Denial of Service (DDoS) attack is a malicious attempt to overwhelm online services with traffic, making it difficult for them to maintain their normal functions. This type of attack has been around since the early days of the internet, with one of the first reported DDoS attacks occurring in 1996.

Botnets are at the heart of most DDoS attacks. A botnet is a network of compromised devices, such as computers or IoT devices, that can be controlled remotely by an attacker. These devices can be used to send large amounts of traffic to a targeted online service, with the goal of overwhelming it and causing it to become unavailable.

Amplification vectors are another key component of DDoS attacks. An amplification vector is a technique used by attackers to increase the amount of traffic they can send to a targeted online service. This is often done by using vulnerable internet protocols or services that can be exploited to send large amounts of traffic. Traffic flooding, which involves sending an excessive amount of traffic to a targeted online service, is another common tactic used in DDoS attacks.

The impact of DDoS attacks can be significant, causing online services to become unavailable or slow, and resulting in financial losses for affected businesses. In addition to the disruption caused by these attacks, they also pose a threat to national security and public safety.

Types of Distributed Denial of Service (DDoS) Attacks

Volumetric DDoS Attacks

Volumetric DDoS attacks are the most common type of DDoS attack, accounting for approximately 80% of all DDoS attacks. These attacks involve overwhelming a targeted system or network with an excessive amount of traffic, typically measured in gigabits per second (Gbps). The goal is to overwhelm the system’s bandwidth and processing capacity, causing it to become unavailable or unresponsive.

In volumetric attacks, attackers use botnets to generate massive amounts of traffic, often by sending numerous packets simultaneously. This type of attack can be particularly devastating for cloud-based services, content delivery networks (CDNs), and other large-scale infrastructure providers.

Protocol-Based DDoS Attacks

Protocol-based DDoS attacks target specific network protocols, such as Transmission Control Protocol (TCP) or User Datagram Protocol (UDP). These attacks exploit vulnerabilities in the protocol itself or its implementation to overwhelm the targeted system. For example, an attacker might send a flood of TCP SYN packets to exhaust the server’s available connections.

These attacks can be particularly challenging to mitigate because they often evade traditional security controls and traffic filtering mechanisms. As a result, specialized solutions are required to detect and block these types of attacks.

Application-Layer DDoS Attacks

Application-layer DDoS attacks target specific web applications or services, such as HTTP, HTTPS, or DNS. These attacks focus on overwhelming the application’s processing capacity, often by sending a large number of requests simultaneously. Unlike volumetric attacks, which primarily target network infrastructure, application-layer attacks aim to disrupt the targeted service itself.

These attacks can be particularly effective in disrupting online businesses and e-commerce platforms, as they can cause significant delays or unavailability of critical services. To mitigate these types of attacks, specialized security solutions must be implemented at the application level.

Motivations Behind Distributed Denial of Service (DDoS) Attacks

Distributed Denial of Service (DDoS) attacks have become increasingly sophisticated, with various motivations driving these malicious activities. In this chapter, we will explore the underlying motivations behind DDoS attacks.

Financial Gain

One primary motivation behind DDoS attacks is financial gain. Criminal organizations and hackers seek to extort money from targeted organizations by launching DDoS attacks, which disrupt business operations and damage reputation. This tactic is often used in ransomware attacks, where attackers demand payment in exchange for ceasing the attack.

For instance, the Mirai botnet was launched in 2016 with the aim of infecting IoT devices and using them to launch massive DDoS attacks against various targets. The attackers demanded a ransom from the targeted organizations, which were forced to pay to prevent further disruption.

Political Activism

Another motivation behind DDoS attacks is political activism. Hacktivists use DDoS attacks as a means of expressing their discontent with governments, corporations, or other entities. These attacks are often launched against websites and services perceived as promoting policies or ideologies opposed to the attackers’ views.

A notable example of this is the 2015 attack on the website of the Turkish Prime Minister’s office by hacktivists opposing the government’s policies. The attack was carried out using a botnet, which flooded the website with traffic, making it unavailable to visitors.

Disruption for Fun

Finally, some individuals engage in DDoS attacks simply for the thrill of causing chaos and disrupting online services. These “script kiddies” may lack the sophistication and resources of professional hackers but can still inflict significant damage.

The 2013 attack on the online gaming platform, League of Legends, is an example of this type of motivation. The attackers used a botnet to flood the website with traffic, causing widespread disruption and frustrating players worldwide.

These motivations demonstrate that DDoS attacks are a multifaceted threat, driven by various factors beyond financial gain alone. Understanding these motivations is crucial for developing effective countermeasures against these malicious activities.

How Distributed Denial of Service (DDoS) Attacks Work

Botnets are created by compromising thousands of vulnerable devices, such as IoT devices, routers, and computers, through malware infections or phishing attacks. These compromised devices, called “zombies” or “bots,” can be controlled remotely to participate in a DDoS attack.

Controlled by Command and Control (C2) Servers The botnets are typically controlled by C2 servers, which send commands to the bots to perform specific actions. The C2 servers act as a central hub, providing instructions on what devices to target, when to start the attack, and how much traffic to generate.

Amplification Vectors To amplify the impact of the DDoS attack, attackers often use amplification vectors such as:

  • NTP (Network Time Protocol) servers
  • DNS (Domain Name System) servers
  • SSDP (Simple Service Discovery Protocol) devices

These targets are vulnerable to specific types of traffic flooding attacks. For example, an attacker can send a small packet to an NTP server and then amplify the response by asking multiple bots to send the same packet back to the target.

Traffic Flooding When the C2 server gives the command, the bots start generating massive amounts of traffic towards the target, overwhelming its resources. This traffic is usually crafted to be as large and complex as possible, making it difficult for the target’s defenses to filter out the legitimate traffic.

Here’s a diagram illustrating the process:

Bot 1 → NTP Server Bot 2 → NTP Server … Target (Victim)

In this example, an attacker uses multiple bots to send small packets to an NTP server. The NTP server responds with large packets, which are then amplified by asking additional bots to send the same packet back to the target.

This results in a massive influx of traffic towards the target, making it difficult for it to maintain its services and respond to legitimate requests.

Defending Against Distributed Denial of Service (DDoS) Attacks

Strategies for Defending Against DDoS Attacks

Traffic Filtering One effective strategy for defending against DDoS attacks is traffic filtering. This involves using firewalls and intrusion detection systems to identify and block malicious traffic patterns. Traffic filtering can be done at various levels, including network-level filtering, transport-layer filtering, and application-layer filtering.

Rate Limiting Another key strategy is rate limiting, which involves setting limits on the amount of traffic that can be sent from a particular source IP address or subnet. This can help prevent an attacker from overwhelming a network with too much traffic.

Network Segmentation Network segmentation is another important defense mechanism. By breaking up a large network into smaller segments, you can limit the spread of a DDoS attack and make it easier to identify and block malicious traffic.

Cloud-Based Services Cloud-based services such as cloud-based content delivery networks (CDNs) and cloud-based security solutions can provide an additional layer of defense against DDoS attacks. These services can help distribute traffic across multiple servers, making it harder for attackers to overwhelm a network with too much traffic.

When implementing these strategies, it’s important to consider the following best practices:

  • Implement rate limiting and traffic filtering at all entry points to the network
  • Use cloud-based services in conjunction with on-premises security solutions
  • Segment networks to limit the spread of DDoS attacks
  • Monitor traffic patterns closely to identify potential threats
  • Collaborate with other organizations to share threat intelligence and improve defenses against DDoS attacks

In conclusion, DDoS attacks are a serious threat that can cause significant disruptions to online services and businesses. By understanding the types of DDoS attacks, their motivations, and how they work, we can better prepare ourselves to defend against these attacks. It is essential to have a robust defense strategy in place, including measures such as traffic filtering, rate limiting, and network segmentation.