Distributed Denial of Service (DDoS) attacks are a prevalent threat in the digital landscape, capable of crippling websites, online services, and even entire networks.

Understanding the different types of DDoS attacks, the tools and techniques attackers use, and the historical examples of such attacks can provide valuable insights into how to defend against them.

A DDoS attack is like a digital traffic jam. Imagine a popular concert venue where a massive crowd of people suddenly tries to get in all at once, not to see the concert but just to block the entrance. This enormous crowd prevents genuine fans from entering and enjoying the show.

In the online world, a DDoS attack works similarly: cyber attackers send a flood of fake traffic to a website or online service, overwhelming it and making it impossible for real users to access.

This fake traffic often comes from a network of hijacked computers called a botnet. The attackers control these compromised machines, instructing them to send large amounts of data to the target site simultaneously.

The site, unable to handle the massive influx, slows down or crashes entirely, similar to how the concert venue gets shut down by the overwhelming crowd. The result is that the website becomes unavailable to everyone, causing frustration and potential losses for the business or service being attacked.

Types of DDoS Attacks

DDoS attacks can be broadly categorized into three types: Volumetric, Protocol, and Application Layer. Each type exploits different aspects of network and application functionality to overwhelm and disable the target.

    Volumetric Attacks

Volumetric attacks are the most common type of DDoS attack. They aim to consume the bandwidth of a target network, making it impossible for legitimate traffic to pass through. This is typically achieved by flooding the target with a massive amount of data.

How it works: Attackers leverage botnets – a network of compromised devices – to generate a high volume of traffic. This traffic can include ICMP (ping) floods, UDP floods, and amplification attacks, where small requests trigger larger responses from the target.

Example: In February 2020, Amazon Web Services (AWS) mitigated a 2.3 Tbps volumetric attack, one of the largest on record, which used a type of amplification attack known as a CLDAP reflection.

    Protocol Attacks

Protocol attacks, also known as state-exhaustion attacks, exploit weaknesses in the protocols used to manage network connections. These attacks aim to exhaust the resources of web servers, firewalls, and load balancers.

How it works: Attackers often use SYN floods, where they send a series of SYN requests to initiate TCP connections but never complete the handshake, leaving the target with open connections that consume resources.

Example: In 2018, GitHub experienced a 1.35 Tbps attack involving the Memcached reflection technique, which exploited a vulnerability in the Memcached protocol to amplify the traffic sent to GitHub’s servers.

    Application Layer Attacks

Application layer attacks target the application itself, rather than the underlying infrastructure. These attacks are more sophisticated and can be harder to detect because they mimic legitimate user behavior.

How it works: Attackers send a high volume of requests to specific application features, such as login pages or search functionalities, overwhelming the server’s ability to respond. HTTP floods are a common method, where attackers send a large number of HTTP requests to the target.

Example: In 2013, a massive DDoS attack hit the financial services industry, targeting banking websites with application layer attacks that caused significant service disruptions.

Tools and Techniques

DDoS attackers use various tools and techniques to execute their attacks, with botnets and amplification attacks being among the most prevalent.

    Botnets

Botnets are networks of compromised devices, often referred to as “zombies,” controlled by an attacker. These devices can be anything from personal computers to IoT devices.

How it works: The attacker uses command-and-control (C2) servers to coordinate the botnet, directing the infected devices to send traffic to the target simultaneously. This makes the attack harder to mitigate, as it originates from many different sources.

Example: The Mirai botnet, which emerged in 2016, leveraged IoT devices to launch record-breaking DDoS attacks against major internet services, including an attack on DNS provider Dyn that took down popular websites like Twitter and Netflix.

    Amplification Attacks

Amplification attacks exploit the functionality of certain protocols to amplify the amount of traffic sent to the target.

How it works: Attackers send requests to open servers that generate larger responses, which are then redirected to the target. Commonly exploited protocols include DNS, NTP, and SSDP.

Example: In 2014, a massive amplification attack using the Network Time Protocol (NTP) targeted Cloudflare, generating 400 Gbps of traffic by exploiting the NTP’s monlist command, which returns a list of recent server requests.

Historical Examples and Their Impacts

Historical examples of DDoS attacks illustrate the severe impact these assaults can have on organizations and internet infrastructure.

    Dyn Attack (2016)

One of the most notable DDoS attacks occurred in October 2016, when the DNS provider Dyn was targeted by the Mirai botnet. The attack disrupted access to major websites like Twitter, Reddit, and Spotify. The sheer scale of the attack, which involved tens of millions of IP addresses, highlighted the vulnerability of critical internet infrastructure to DDoS assaults.

    GitHub Attack (2018)

In February 2018, GitHub, a popular code hosting platform, was hit by a 1.35 Tbps DDoS attack, which was the largest ever recorded at the time. The attack utilized the Memcached amplification technique, showcasing the potential for new methods to generate unprecedented volumes of traffic. GitHub’s quick response and mitigation strategies prevented prolonged downtime, but the incident underscored the evolving nature of DDoS threats.

Understanding the mechanics and methods of DDoS attacks is crucial for developing effective defenses. By recognizing the different types of attacks and the tools and techniques used by attackers, organizations can better prepare for and mitigate these disruptive threats.

[INTEL : Conducting Your Own Cybersecurity Audits]