What Is a DDoS Attack?

Downtime is no longer just inconvenient. It is expensive, disruptive, and damaging to brand trust. One of the most common causes of sudden outages today is the distributed denial of service, or DDoS, attack.

A DDoS attack is a deliberate attempt to overwhelm an organization’s systems by flooding them with internet traffic. By using thousands or even millions of devices around the world, attackers generate so much fake traffic that legitimate users can no longer access websites, applications, or services.

These attacks are favored by cybercriminals because they are inexpensive to launch, easy to scale, and capable of causing major damage in a short period of time. Whether the motive is extortion, political protest, or simple disruption, the impact can be severe.

In this article, we will explore what a DDoS attack is, how it works, the different types of attacks, the damage they cause, and how organizations can prevent and respond to them.

DDoS attack explained

DDoS stands for Distributed Denial of Service. It is a type of cyberattack in which an attacker uses multiple computers or connected devices, often part of a botnet, to flood a server, website, or network with traffic. The goal is to exhaust system resources such as bandwidth, memory, or CPU capacity so that legitimate users cannot access the service.

Unlike a traditional denial of service (DoS) attack, which originates from a single system, a DDoS attack distributes the traffic load across many systems. This makes it harder to block and much more difficult to trace. Attackers frequently rely on botnets made up of compromised devices, including home routers, IoT hardware, and vulnerable servers.

The targets of DDoS attacks vary widely. Some attackers go after high-profile websites or financial institutions. Others target APIs, cloud infrastructure, or DNS services. In some cases, the attackers seek ransom payments. In others, they may simply want to cause chaos or damage a competitor’s operations.

DDoS attacks are also sometimes used as a distraction. While defenders focus on restoring service, attackers may exploit unrelated vulnerabilities to deliver malware or steal data.

Types of DDoS attacks

DDoS attacks come in multiple forms. Most fall into one of three broad categories, each with its own characteristics and methods of disruption.

Volume-based attacks
These attacks rely on sending massive amounts of data to overwhelm the target’s bandwidth. The sheer volume of traffic consumes all available internet capacity, making services unreachable.

Common examples include:

• UDP floods, which send large numbers of connectionless packets to random ports
• ICMP floods, which overload systems with ping requests
• Amplification attacks, where small requests to misconfigured servers result in large replies sent to the target

Protocol attacks
Protocol-based attacks exploit weaknesses in the infrastructure that supports internet communications. These attacks focus on exhausting the capacity of network devices such as firewalls, load balancers, and routers.

Examples include:

• SYN floods, which disrupt the TCP handshake by sending a high volume of incomplete connection requests
• Ping of Death, which crashes systems by sending oversized or fragmented packets
• Smurf attacks, which use spoofed IP addresses to trigger large responses from entire networks

Application layer attacks
These attacks target the application layer, where services like websites and APIs operate. They are designed to exhaust server resources by mimicking real user behavior. Although these attacks may involve less bandwidth, they are harder to detect and mitigate.

Imagine a train station with just one ticket kiosk. This kiosk serves customers one at a time. Normally, people walk up, quickly request a ticket, and move on. The system runs smoothly.

Now imagine dozens of fake customers show up. Each one walks to the kiosk, starts asking complicated questions, then pauses, checks their bag, steps aside, comes back, asks something else and never actually buys a ticket. These fake customers never leave, and they keep cycling through, making the line longer and longer.

Meanwhile, real travelers are stuck outside. They cannot get tickets, even though the kiosk is technically still working. It is just so busy with fake interactions that it cannot serve anyone else.

That is how an application-layer DDoS attack works. It overwhelms systems by mimicking legitimate users and consuming all available resources without doing anything meaningful. The server stays online, but it becomes too bogged down to function.

Examples include:

• HTTP GET/POST floods, which flood web servers with requests that appear valid
• Slowloris, which keeps server connections open indefinitely by sending partial HTTP headers
• DNS query floods, which overwhelm name servers with a high volume of requests

Most modern DDoS attacks combine multiple types in a single campaign. These multi-vector attacks are harder to defend against and require layered defenses across network, application, and endpoint layers.

How DDoS attacks work

A DDoS attack is not a random event. It involves a series of planned steps that turn compromised devices into tools for disruption.

Step 1: Building a botnet
Attackers first assemble a network of infected devices, often referred to as a botnet. These devices may include personal computers, smart home devices, cameras, or servers that have been compromised by malware. Many users are unaware that their systems have been hijacked and are being used in attacks.

Step 2: Establishing control
The attacker communicates with the botnet through a command and control (C2) system. This allows them to coordinate the timing, size, and nature of the attack. The C2 system may be centralized or spread across multiple relay points to make takedown more difficult.

Step 3: Generating traffic
Once activated, the bots begin sending traffic to the chosen target. The type of traffic depends on the method of attack. Some bots might flood the network with raw packets. Others might simulate real users accessing a website or requesting information through an API.

Step 4: Overwhelming the target
As the volume of traffic increases, the target system begins to struggle. Websites may slow down or crash. APIs might return errors. Network devices may be pushed beyond capacity, making it difficult to filter out legitimate requests from malicious ones.

Step 5: Escalation and duration
Some attackers keep pressure on their target for a short time to make a point or test defenses. Others may sustain the attack for hours or days. In many cases, attackers change their tactics during the campaign, switching from one method to another to bypass defenses and stay ahead of mitigation strategies.

Impacts of a DDoS attack

The effects of a DDoS attack go far beyond slow websites. They often ripple through business operations and customer experiences.

Downtime and disruption
The most immediate impact is loss of availability. Websites go offline, services stop responding, and customers cannot access critical systems. For e-commerce and SaaS providers, even a few minutes of downtime can translate to lost sales and damaged trust.

Financial loss
The costs of a DDoS attack can include more than lost revenue. Organizations often face additional bandwidth charges, incident response expenses, and long-term infrastructure upgrades. In some cases, attackers demand ransom payments to stop the attack.

Reputational harm
Customers expect reliable digital services. When those services are interrupted, trust erodes quickly. Public attacks may also attract media attention and damage brand reputation.

Operational stress
While IT teams scramble to restore services, other business functions may come to a halt. Internal collaboration tools, remote access platforms, and customer support channels may be affected, slowing productivity across departments.

Hidden security risks
DDoS attacks are sometimes a distraction. While defenders are busy handling the volume of traffic, attackers may use the opportunity to breach other parts of the network, plant malware, or steal data.

Detection and prevention

Stopping a DDoS attack requires both early detection and layered defenses that absorb, redirect, or filter malicious traffic before it reaches critical systems.

Monitoring traffic in real time helps establish a baseline of normal behavior. When sudden spikes occur or patterns shift in ways that do not align with legitimate usage, this can signal the early stages of a DDoS campaign. Behavioral analysis tools and log visibility are key to spotting those deviations.

Rate limiting and traffic filtering can reduce the impact of many attacks. By capping how many requests a system accepts from a single IP or region, organizations can prevent abuse while allowing legitimate users to connect. Filters can also block traffic from suspicious or known-malicious sources.

Web application firewalls (WAFs) protect Layer 7 services by inspecting HTTP traffic and blocking abusive patterns like form floods or repetitive requests. When configured properly, a WAF can identify bots pretending to be real users and shut them out.
DNS protection is critical as attackers often attempt to overwhelm name servers. Managed DNS providers with built-in DDoS filtering and geographic load balancing can help organizations withstand these types of attacks.

Content delivery networks (CDNs) improve performance but also provide a layer of protection. By distributing traffic across global edge servers, CDNs absorb bursts and keep origin servers from being overwhelmed.

Cloud-based mitigation services are a strong option when attacks exceed the bandwidth or filtering capabilities of on-premise systems. These platforms specialize in handling large-scale attacks and can reroute, scrub, and return clean traffic with minimal delay.

Lastly, organizations should secure their own systems to avoid becoming part of someone else’s botnet. Keeping firmware updated, using strong passwords on IoT devices, and monitoring for unusual outbound traffic all reduce the risk of being weaponized in a larger attack.

AI’s role in DDoS attacks

Artificial intelligence has added new dimensions to both attacking and defending in the DDoS landscape.

On the offensive side, attackers can use AI to generate more realistic traffic. Botnets can now mimic human behavior, rotating IP addresses, adjusting click rates, and even responding to basic security challenges. These behaviors make it harder for defenses to distinguish fake traffic from real users.

Defenders are also using AI to stay ahead. Machine learning models can scan live traffic for anomalies, comparing requests to historical behavior and flagging anything unusual. This includes recognizing subtle indicators such as request headers, session patterns, or the frequency of page reloads.

AI also helps automate response. When abnormal activity is detected, automated systems can reroute traffic, apply new filtering rules, or trigger alerts to human operators. These responses happen faster than any manual process and can keep services available during the early moments of an attack.

As attacks become more complex, organizations that adopt AI-assisted defenses gain valuable speed and accuracy in their response.

Responding to a DDoS attack

Responding to a live DDoS attack requires coordination, clear communication, and decisive action.

First, the attack must be confirmed and analyzed. Security and network teams should review real-time telemetry to determine what systems are being targeted, where the traffic is coming from, and what type of DDoS vector is in play. Knowing whether it's a Layer 3 flood or a Layer 7 HTTP surge shapes the response.

Next, internet service providers and cloud vendors should be notified. Many have built-in mitigation features or can assist in rerouting traffic. If a third-party DDoS mitigation service is already in place, this is the time to activate protection and begin filtering.

At the same time, defenders may choose to apply filters, rate limits, or geographic blocks to buy time and preserve uptime for legitimate users. In some cases, services may be temporarily shifted to a backup environment or edge-hosted fallback page.

Clear communication matters. Internal stakeholders should be briefed, and customers should be notified if services are degraded. Silence during an outage often causes more damage than the downtime itself.

After the attack ends, teams should conduct a full review. What was targeted, how did defenses hold up, and what should be improved? This review helps refine the response plan and strengthens protection for the next incident.

Notable case studies

The Dyn DNS attack in 2016 used the Mirai botnet to take down one of the internet’s most critical service providers. By leveraging millions of infected IoT devices, attackers disrupted access to major platforms including Twitter, Netflix, and Spotify. The attack revealed how poorly secured home hardware could be used to disrupt global infrastructure.

In 2018, GitHub was targeted by what was, at the time, the largest recorded DDoS attack. Peaking at 1.35 terabits per second, the attack used Memcached servers to amplify traffic. GitHub’s upstream provider mitigated the attack in under ten minutes by rerouting and filtering at scale. This event became a case study in successful cloud-based DDoS response.

Estonia experienced one of the earliest politically motivated cyberattacks in 2007. Government websites, media outlets, and banks were targeted with sustained DDoS campaigns. The disruption impacted national operations and demonstrated how DDoS could be used as a geopolitical weapon.

A midsized e-commerce company preparing for a major product launch experienced a targeted Layer 7 DDoS attack. The company had no mitigation strategy in place, but within an hour, traffic was redirected through a managed cloud scrubbing service. Filtering rules blocked abusive patterns while allowing real customers through. The site remained stable for the remainder of the launch, avoiding financial loss and customer frustration.

Conclusion

DDoS attacks are one of the most accessible and disruptive tools in the hands of today’s cyber adversaries. They do not require deep technical skill to launch, and for a relatively small cost, they can bring down websites, freeze services, and damage brands.

Fortunately, these attacks are not unstoppable. With the right visibility, layered defenses, and tested response plans, organizations can absorb, deflect, or neutralize the impact of even large-scale campaigns.

Mitigation begins with preparation. Network monitoring, DNS redundancy, cloud-based filtering, and security-aware infrastructure all reduce risk. For small and mid-sized businesses, managed services offer expert-level response without the overhead of building a full security team.

No organization is too small to be targeted. Whether used as extortion, retaliation, or a diversion, DDoS remains one of the most common attack types across every industry. Organizations that prepare for it are better positioned to protect their operations, customers, and reputation when the next wave hits.