What is a DDoS Attack and How to Prevent It

In the last quarter of 2023 alone, DDoS attacks witnessed a staggering 117% increase, emphasizing the urgency for robust cybersecurity measures. Cloudflare, a leader in the field, automatically tackled around 996 attacks per hour, with 27 terabytes of data. AI played a crucial role in simplifying and reducing these attacks, making them less reliant on numerous machines.

In this blog post, we will discuss what a DDoS attack is, how it works, the types of DDoS attacks, how to identify a DDoS attack and most importantly, how to prevent one.

What is a DDoS Attack?

A Distributed Denial-of-Service (DDoS) Attack is a malicious attempt to disrupt normal traffic to a server or network, rendering it inaccessible to its users. A DDoS attack floods the server or network with more traffic than it can handle, causing the server to crash.

DDoS attackers usually use compromised computers, known as bots, which will be used to send traffic to the targeted server or network simultaneously.

How Does a DDoS Attack Work?

DDoS attacks employ networks of compromised machines, controlled remotely by attackers. It operates by overloading a network or server with a high volume of traffic that the network cannot accommodate. The attack is executed using a network of Internet-connected machines, including computers and IoT devices, that have been infected with malware.

This traffic is sent by malicious actors who use botnets to send the same traffic to the target from multiple sources at the same time. The target server or network is then bombarded with requests from each bot, which can overwhelm the system and lead to a denial of service for regular traffic.

The complexity of a DDoS attack lies in the fact that each bot is a legitimate Internet device, making it challenging to distinguish between normal and malicious traffic. This characteristic makes DDoS attacks incredibly potent, as they can effectively disrupt a system and complicate the mitigation process.

Types of DDoS Attacks

DDoS attacks can be categorised into three types:

• application layer attacks,
• protocol attacks, and
• volumetric attacks.

Each targets different components of a network connection, exploiting vulnerabilities in layers 3, 4, and 7 of the OSI model.

Application Layer Attacks

Application Layer Attacks, also known as Layer 7 DDoS attacks, are designed to overwhelm a target's resources, ultimately causing a denial-of-service. These attacks focus on the layer where web pages are created and delivered in response to HTTP requests.

While a single HTTP request is relatively inexpensive to execute from the client side, it can be quite resource-intensive for the target server. The server often has to load multiple files and run various database queries to generate a web page, making it susceptible to exhaustion under high volumes of such requests.

The modus operandi of such an attack can be likened to repeatedly pressing refresh in a web browser on numerous computers simultaneously. This results in a flood of HTTP requests that can overwhelm the server, leading to a denial-of-service.

These attacks can range from simple to complex. In simpler versions, the attack might involve accessing a single URL using the same range of attacking IP addresses, referrers, and user agents. On the other hand, more complex versions could employ a wide variety of attacking IP addresses and randomly target URLs using a diverse set of referrers and user agents.

Protocol Attacks

Protocol attacks, also known as state-exhaustion attacks, are designed to disrupt service by over-consuming the resources of servers and network equipment such as firewalls and load balancers. These attacks exploit vulnerabilities in layer 3 and layer 4 of the protocol stack to make the target inaccessible.

A common form of protocol attack is a SYN flood, which takes advantage of the TCP handshake mechanism, the initial sequence of requests that two computers use to establish a network connection. The attack can be likened to a worker in a supply room receiving an overwhelming number of unconfirmed package requests, resulting in the worker becoming inundated and unable to respond to new requests.

In a SYN flood, the attacker sends a large volume of TCP "Initial Connection Request" SYN packets to the target, using spoofed source IP addresses. The targeted machine responds to each of these connection requests and waits for the final step of the handshake, which never comes. As a result, the target's resources become exhausted trying to complete these never-ending requests, leading to a disruption in service.

Volumetric Attacks

Volumetric Attacks are a type of DDoS attack that aims to cause congestion by consuming all available bandwidth between the target and the broader Internet. The attacker floods the network with an overwhelming amount of data, often using a form of amplification or massive traffic generation techniques like requests from a botnet.

A common example of a volumetric attack is a DNS amplification. In this scenario, the attacker uses an open DNS server to flood the target with data. This can be compared to a situation where someone calls a restaurant, orders everything on the menu, and asks for a callback to repeat the entire order - except the callback number provided belongs to the unsuspecting victim. With minimal effort from the caller, the victim receives a lengthy response.

In the context of a DNS amplification attack, the attacker sends a request to an open DNS server but spoofs the IP address, making it appear as if the request came from the victim's IP address. As a result, the server's response, which is significantly larger than the original request, is sent to the victim. This creates a surge of unwanted network traffic that can lead to severe network congestion and service disruption.

How to Identify a DDoS Attack

It is not always easy to identify a DDoS attack since it can look like a regular traffic spike. However, there are specific tell-tale signs that can give you a hint that a DDoS attack is happening.

The most prominent symptom of a DDoS attack is a sudden decrease in the speed of a site or service or it becoming completely unavailable. However, other factors such as a legitimate surge in traffic can also cause similar performance issues, necessitating further investigation.

Traffic analytics tools can assist in identifying some key indicators of a DDoS attack, such as:

• An abnormally large amount of traffic originating from a single IP address or IP range.
• A surge in traffic from the same device type, geolocation, or web browser version.
• Unusual traffic spikes at odd hours of the day or patterns that appear unnatural.

These are general signs, but there can be other, more specific indicators of a DDoS attack, which can vary based on the type of attack.

How to Prevent DDoS Attacks

There are several methods used to prevent DDoS attacks, and they include:

1. Implementing firewalls, intrusion prevention systems, and other security measures to monitor and filter incoming network traffic.

2. Work with your internet service provider (ISP) to create DDoS prevention strategies that can filter out malicious traffic before it reaches your server or network.

3. Use a Content Delivery Network (CDN) that can spread incoming traffic across different servers to prevent overloading a single server.

4. Always keep your software and security measures updated to prevent attackers from exploiting known vulnerabilities in your system.

How to Mitigate a DDoS Attack

Mitigating DDoS attacks requires differentiating between attack and normal traffic. Various strategies, including blackhole routing, rate limiting, web application firewalls, and Anycast network diffusion, can be employed.

A layered approach is crucial for countering multi-vector attacks, where multiple trajectories are targeted simultaneously. Make sure to download our free guide on DDoS Attack Mitigation.

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The Threat is Real

DDoS attacks are a real threat that could render your servers or network inaccessible and cause severe financial ramifications. It is, therefore, crucial to take sufficient precautions by implementing robust security systems to safeguard your servers or networks from potential DDoS attacks.

By implementing firewall systems, working with a provider to filter malicious traffic, using a CDN, and updating your systems, you can significantly reduce the risk of a successful DDoS attack. Always make sure to remain vigilant and take preventative measures, to stay one step ahead of attackers.

Don't wait for the storm; be prepared. Explore Cogify's cybersecurity services now and safeguard your digital future. Contact Us for a Consultation.

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