What is a DDoS Attack?

Service availability has become as critical as security itself. For organizations, even a few minutes of downtime can translate into significant financial loss, customer dissatisfaction, and reputational damage. Among the most persistent and disruptive threats to availability are Distributed Denial of Service (DDoS) attacks — large-scale assaults designed to overwhelm systems and render services inaccessible.

Unlike stealthy cyber intrusions that aim to exfiltrate data, DDoS attacks focus on one simple goal: disruption. They exploit the openness of the internet, harnessing thousands or even millions of compromised devices to flood a target with malicious traffic. The result can range from temporary service degradation to complete shutdown of business-critical platforms.

For companies, understanding how DDoS attacks work is essential for effectively protecting infrastructure and maintaining business continuity. This article explores the mechanics of DDoS attacks, their motivations, real-world cases, and best practices for mitigation.

Definition of a DDoS Attack

DDoS attack is a targeted attempt to disrupt the normal functioning of a network, service, or application by overwhelming it with a flood of malicious traffic. Unlike a typical hardware or software failure, which can cause downtime by accident, DDoS attacks are deliberate acts aimed at making resources inaccessible to legitimate users. 

The ultimate goal is to exhaust bandwidth, CPU power, memory, or application-level resources until the target system cannot respond properly. These attacks are designed to cause major disruptions, making websites and applications unavailable to users by overwhelming them with a flood of malicious traffic. DDoS attacks have become more frequent and sophisticated, with attackers leveraging vast botnets to launch large-scale operations that are difficult to defend against.

DoS vs. DDoS

To understand a DDoS attack, it helps to compare it with a traditional Denial of Service (DoS) attack. In a DoS scenario, a single machine generates malicious traffic directed at the victim. This makes DoS attacks relatively easier to detect and block, since traffic comes from identifiable origins. However, they are also limited in scale, as the attacking machine has finite bandwidth and computational resources.

DDoS attacks, by contrast, rely on distributed networks of compromised devices, often referred to as botnets. These botnets consist of thousands, sometimes millions, of infected endpoints such as personal computers, servers, IoT devices, or even industrial systems. Because traffic originates from many geographically dispersed sources, filtering malicious requests becomes significantly more complex. Blocking one IP address or network segment has little effect, as the attack continues from countless others.

Another critical distinction is the method of attack. A DoS attack doesn’t rely on flooding a server with useless traffic; instead, it exploits vulnerabilities and flaws in the system. For instance, an attacker might trigger a resource-intensive action on the server, such as uploading a file that takes an extraordinarily long time to process or initiating a request that consumes excessive compute power. While these attacks can be blocked by identifying and denying access to the attacker, the better approach is to address the underlying vulnerabilities. 

This can be achieved by implementing rate-limiting for compute-heavy operations and regularly patching vulnerabilities to prevent abuse. In contrast, DDoS attacks, which involve distributed networks of compromised devices, are harder to mitigate with traditional methods and require more sophisticated approaches like cloud-based scrubbing centers, Anycast routing, and advanced behavioral analytics to effectively separate legitimate user requests from malicious traffic at scale.

Why Attackers Use DDoS

Attackers do not always seek financial gain directly; sometimes disruption itself is the objective. Nevertheless, in the majority of cases, the underlying driver can be grouped into several recurring categories.

Extortion is one of the most common motives behind DDoS attacks. In these cases, attackers threaten organizations with prolonged downtime unless a ransom is paid, typically in cryptocurrency. Ransom DDoS (RDDoS) attacks take advantage of the fact that service availability is a visible and critical factor for many businesses. Even a few hours of downtime can result in significant losses, particularly for companies that rely heavily on digital services like e-commerce platforms or financial systems. Often, the pressure to pay comes not from the cost of recovery but from the immediate impact on business operations.

Hacktivism is another common motivator. Attackers driven by political or social causes may target organizations whose actions, values, or affiliations they oppose. Unlike extortion, the goal is not financial gain but rather disruption and visibility. These attacks are often aimed at making a statement by bringing attention to a cause, using a high-profile outage as a means to communicate their message.

Cyber warfare represents a more organized, coordinated form of attack, often involving groups with significant resources. While usually associated with larger-scale operations, these attacks aim to disrupt critical infrastructure, communication channels, or services that could interfere with or destabilize an adversary’s systems. In this case, the attackers may not be seeking immediate financial rewards, but rather seeking to achieve broader strategic objectives through sustained disruption. These attacks are often highly sophisticated and difficult to mitigate.

Cyber vandalism involves attacks that are carried out for no other reason than to create chaos or to showcase one’s technical abilities. Often, individuals or small groups will launch DDoS attacks simply for notoriety, entertainment, or as a way to demonstrate their skills. The widespread availability of DDoS-for-hire services makes it easy for non-technical actors to launch significant attacks with minimal effort.

How DDoS Attacks Work

While the effects of a DDoS attack are immediately visible — websites going offline, services timing out, applications failing to respond — the underlying mechanics involve several stages. Attackers do not simply press a button; successful campaigns are usually the result of careful preparation and the exploitation of technical weaknesses. Let’s take a look at the main steps:

1. Botnet creation. Attackers compromise vulnerable devices across the internet, often exploiting weak passwords, outdated software, or unpatched vulnerabilities. IoT devices such as cameras, routers, and sensors are particularly attractive, as they are widely deployed and often lack proper security hardening. Once compromised, these devices become part of a larger network under the attacker’s control. Through command-and-control servers, the attacker can coordinate the botnet to act in unison.
2. Launching the attack. At a designated time, the attacker instructs thousands or millions of bots to simultaneously send traffic toward the target. This flood can take many forms: raw network packets, HTTP requests, or even carefully crafted queries designed to exhaust application resources. Because the traffic originates from diverse, legitimate-looking sources, traditional perimeter defenses such as firewalls or intrusion prevention systems are easily overwhelmed.
3. Flooding the network. The actual impact of a DDoS campaign depends on the attack vectors, which can be mapped to different layers of the OSI model. At the network layer (Layer 3/4), attackers may generate massive volumes of traffic, such as UDP floods or SYN floods, designed to consume bandwidth or exhaust server TCP/IP stacks. At the transport and session levels, these floods can cause systems to hang under the sheer number of half-open or malformed connections.
4. Application layer attacks. At Layer 7, attacks are more subtle. Instead of raw bandwidth exhaustion, attackers mimic legitimate user behavior, such as sending thousands of concurrent HTTP requests or database queries. These Layer 7 attacks are harder to detect, as they resemble normal traffic patterns but are designed to consume disproportionate amounts of server processing power.
5. Hybrid attacks. It often combines multiple vectors across layers, making them harder to mitigate. For example, a campaign might begin with a volumetric flood at the network level to distract defenses, followed by a precise application-layer attack aimed at the core service logic.

Common Types of DDoS Attacks

DDoS attacks are not all alike. They vary in method, target layer, and impact, making it essential for organizations to understand the most common categories. Broadly, DDoS attacks are classified into volumetric attacks, protocol attacks, and application-layer attacks. Each category exploits different weaknesses in network infrastructure and applications.

Volumetric Attacks

These aim to overwhelm a target’s bandwidth capacity by generating massive amounts of traffic. Because the attacker’s goal is simply to flood network pipes, volumetric attacks are often the largest in scale.

• UDP floods: Exploit connectionless UDP by sending large volumes of datagrams, forcing the target to process and reply to non-existent requests.
• ICMP floods: Overuse ICMP echo requests (pings) to saturate bandwidth.
• DNS amplification: Abuse open DNS resolvers by sending small queries with a spoofed IP, leading to disproportionately large responses directed at the victim.
• NTP amplification: Leverages misconfigured Network Time Protocol servers for large amplified responses.
• Memcached amplification: Abuses publicly exposed memcached servers to generate responses amplified by factors of hundreds, making it one of the most destructive techniques.

Protocol Attacks

These exploit weaknesses in network protocols or server resources, aiming to exhaust firewalls, load balancers, or connection tables rather than raw bandwidth.

• SYN floods: Exploit the TCP handshake by sending numerous SYN requests without completing connections, leaving servers overloaded with half-open sessions.
• Fragmented packet attacks: Send malformed or oversized packet fragments that force the target to waste resources on reassembly.
• Smurf attacks: Use ICMP echo requests directed at broadcast addresses with a spoofed source, causing many hosts to respond simultaneously to the victim.
• Ping of Death: Sends oversized ICMP packets that can crash or destabilize systems unable to handle them.

Application-Layer Attacks

These focus on Layer 7 of the OSI model, targeting the application logic rather than bandwidth or protocols. They are often stealthy, harder to detect, and mimic legitimate user behavior.

• HTTP(S) floods: Overwhelm web servers with GET or POST requests, appearing similar to real user traffic.
• Low-and-slow attacks (e.g., Slowloris): Keep connections open for long periods with minimal data transfer, gradually exhausting server threads.
• GET/POST floods: Send repeated requests for resource-intensive pages or database queries to drain application resources.

Because each type of attack targets different vulnerabilities, modern DDoS campaigns often combine multiple attack vectors simultaneously to maximize disruption and evade defenses.

Anti-DDoS Protection

Mitigating DDoS attacks requires a layered approach, as no single technique can stop every vector. Defenses range from basic traffic filtering to global-scale cloud mitigation services, depending on the size and sophistication of the attack.

Upstream Rate Limiting and Blackholing

• Rate limiting: Configures routers or firewalls to limit the number of requests allowed per second, preventing sudden spikes from overwhelming services.
• Blackholing (null routing): Routes all traffic to a non-existent address, effectively dropping it. This stops the attack traffic but also sacrifices legitimate traffic to the target.
• Traffic scrubbing: Redirects traffic through dedicated scrubbing centers where malicious packets are filtered out before reaching the target.

Cloud-Based and Edge Solutions

Uses globally distributed nodes to absorb and filter attack traffic closer to its source, reducing pressure on the target’s infrastructure.

Global CDN providers offer built-in DDoS mitigation that leverages their massive networks to distribute and filter malicious traffic. These solutions are especially effective for volumetric and protocol-based floods.

Application-Layer Defenses

Because application-layer attacks mimic real users, specialized defenses are necessary:

• Web Application Firewalls (WAFs): Filter requests based on rulesets, blocking suspicious or malicious patterns.
• CAPTCHA challenges: Differentiate between human users and automated bots attempting to flood servers.
• Rate-limiting at Layer 7: Restricts the number of requests per user/IP for specific endpoints.
• Fingerprint-based filtering: Identifies malicious clients by behavioral patterns, device fingerprints, or anomalous request signatures, providing more adaptive filtering than static IP blocking.

In practice, effective DDoS protection combines all three layers. Basic rate limiting handles low-level floods, cloud-based scrubbing absorbs large-scale volumetric attacks, and WAFs/CAPTCHAs mitigate stealthy Layer 7 assaults. For organizations choosing an IaaS provider, evaluating the breadth of their anti-DDoS infrastructure — from upstream scrubbing to application-layer protection — is critical for ensuring resilience against diverse threats.

Best Practices and Recommendations

Protecting against DDoS attacks requires more than a single defensive tool — it demands a multi-layered strategy that adapts to evolving threats. Organizations that rely on digital infrastructure should focus on combining network-level defenses, application-level protections, and external intelligence sources.

A resilient security posture begins with ensuring redundancy and high availability across infrastructure. By deploying resources across multiple regions and using load balancers, companies can reduce the risk that a single point of failure will be overwhelmed by malicious traffic. At the network layer, automated mitigation mechanisms, such as rate limiting and upstream filtering, should be configured to block obvious floods before they reach applications.

Equally important is threat intelligence. Staying informed about the latest botnets, amplification techniques, and industry-wide attack patterns enables faster detection and more proactive defenses. Some IaaS providers offer integrated DDoS protection with real-time monitoring, leveraging global traffic visibility to identify anomalies at scale.

Collaboration also plays a crucial role. Enterprises benefit from working closely with ISPs, content delivery networks (CDNs), and cloud security providers, who often have more extensive bandwidth and scrubbing capabilities than a single organization can maintain. Regular testing — through simulated attack exercises and red-team assessments — ensures defenses are not only deployed but also effective when needed.

Ultimately, a defense-in-depth strategy supported by continual updates, monitoring, and external partnerships is the only way to maintain resilience against increasingly sophisticated DDoS campaigns.

Real-World Examples

Several high-profile DDoS incidents illustrate the scale and impact these attacks can have, even on some of the most technologically advanced organizations.

One of the largest documented DDoS attacks occurred against Cloudflare in 2022, when the company mitigated a 26 million request-per-second HTTPS flood generated by a botnet of only 5,000 devices. This attack highlighted how even small, distributed botnets can leverage amplification to extraordinary effect.

Another significant case was the Dyn DNS outage in 2016, caused by the Mirai botnet. The attack temporarily brought down major services including Twitter, Netflix, and Reddit, demonstrating the fragility of core internet infrastructure when targeted at the DNS layer.

The Mirai botnet itself became one of the most infamous examples of IoT-driven DDoS campaigns. By exploiting weakly secured connected devices such as cameras and DVRs, attackers built a massive botnet that was capable of launching attacks exceeding 1 Tbps in 2016 — unprecedented at the time.

More recently, Tier-1 networks — the backbone providers of the internet — have reported DDoS events exceeding 3 Tbps, forcing the industry to adopt global-scale scrubbing centers and Anycast routing to distribute and absorb such immense traffic volumes.

These examples underscore the fact that DDoS attacks are not theoretical threats — they are real, recurring, and escalating in scale. They also demonstrate why enterprises must evaluate their IaaS providers not only on performance but also on the strength of their integrated DDoS defenses.

Conclusion

DDoS attacks remain one of the most disruptive threats in the cybersecurity landscape, capable of taking down critical services within minutes. Their evolving scale and complexity mean that defending against them requires more than isolated tools — it demands a multi-layered strategy combining robust infrastructure, intelligent traffic management, and proactive monitoring.

For enterprises, the choice of provider plays a central role in mitigating this risk. A reliable partner should not only deliver compute and storage resources but also embed advanced anti-DDoS protections, redundancy, and real-time threat intelligence into its services.

Servercore’s solutions includes basic DDoS protection at L3-L4 layers, ensuring a first layer of defense against common network-level attacks. The platform’s security approach combines network isolation, compliance with international standards like PCI DSS, and multi-layered infrastructure protection.

In practice, this means Servercore customers gain both availability and confidence: their workloads benefit from foundational DDoS protection, while comprehensive security measures help maintain service continuity.