A Distributed Denial of Service (DDoS) attack is a cyber threat aimed at disrupting the normal operation of a targeted server, service, or network by overwhelming it with an enormous amount of traffic.
This malicious activity is usually carried out using a network of compromised devices, known as a botnet, to flood the target with excessive traffic, making it impossible for legitimate users to access the service.
DDoS attacks can have serious consequences, including downtime, financial loss, and damage to a company’s reputation, making effective mitigation strategies essential for protecting online resources.
Quick Facts:
- DDoS attacks have grown by 49% in Q3 2024, with recent incidents hitting an all-time high of 4.2 terabits per second.
- Data from Microsoft revealed that the United States was the top target for DDoS attacks on Microsoft services, followed by India.
- Ransomware groups such as BlackCat, REvil, Suncrypt, and AvosLocker have recently been observed using DDoS cyber extortion campaigns.
What is a DDoS Attack?
A distributed denial-of-service (DDoS) attack is a cyber-attack where an attacker floods a website, server, or network resource with excessive malicious traffic. This overwhelming surge causes the target to crash or become unresponsive, blocking legitimate users from accessing the service.
Think of a DDoS attack as if hundreds of fake customers suddenly overwhelmed a popular coffee shop. These customers don’t order anything—they just take up space, form long lines, and occupy all the seats. This prevents real customers from entering, ordering coffee, or getting seats. Similarly, a DDoS attack clogs up a server or network, stopping legitimate users from accessing the needed services.
A DDoS attack targeting a company’s website, web application, APIs, network, or data center infrastructure can cause downtime and block legitimate users from purchasing, accessing services, retrieving information, or using other resources.
How Does a DDoS Attack Work?
Most DDoS attacks are carried out using botnets, networks of compromised computers working together. These machines all try to access a website simultaneously, overwhelming the server and causing it to crash.
So, how do hackers create these botnets? They hijack other computers by exploiting malware or unpatched vulnerabilities on someone else’s server, gaining control through Command and Control (C2) software. This allows them to assemble large botnets cheaply and easily, which can be used for malicious purposes.
Once the hackers have control of enough machines, they can issue commands to the entire botnet, causing all the computers to flood the target server. This mass traffic often results in server outages and disruptions, leading to significant downtime.
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How to identify a DDoS attack?
1. Slow Down Website Performance
One of the earliest warning signs is your website, app, or API becoming unusually slow or unresponsive. Pages may take longer to load, certain features might stop working, or users could report difficulties completing actions like purchases. These issues may start intermittently but often escalate into prolonged downtime.
2. Database Connectivity Issues
Problems connecting to your database can also signal an attack. Applications might struggle to connect or connections might drop unexpectedly, resulting in error messages or timeouts visible to both system logs and end users.
3. Network Connectivity Issues
Frequent disconnections or unstable internet connectivity can also indicate an attack. If multiple services experience outages at the same time, it’s likely a broader DDoS attack rather than an isolated technical glitch.
4. Unusual Server Resource Usage
During a DDoS attack, your server’s resources often behave abnormally. CPU and memory usage might spike without an increase in legitimate traffic. Network bandwidth may also hit unusually high levels, causing your server to slow down or become unresponsive.
5. Suspicious Traffic Patterns
Look for sudden spikes in traffic that don’t align with normal user behavior. This traffic may originate from unfamiliar geographic locations or show patterns like thousands of requests with identical user agents, indicating a coordinated attack.
6. Application-Level Anomalies
Specific features of your application may act up before other symptoms appear. For example, you might see a spike in failed login attempts, abandoned shopping carts, or API errors. These could indicate attackers targeting specific functions of your site.
7. Communication System Disruptions
Your email, instant messaging, or VoIP systems may show signs of overload, such as delays or failures. These disruptions often occur alongside other symptoms as attackers overwhelm your network.
Types of DDoS Attacks
| DDoS Attack Type | Category | Characteristics | Examples |
| Application layer attack | Connection-based | Difficult to detect | SQL injection, XSS |
| Protocol Attack | Connection-based | Attacks the network layer | SYN flood, ping of death |
| Volumetric attacks | Connectionless | High volume, using bots | UDP flood |
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Application vulnerability attacks
Application vulnerability attacks, or Layer 7 attacks, target the application layer of a network. These attacks exploit weaknesses in the software or services running on a server, causing it to use up its resources like CPU, memory, or database connections.
Some common attacks include sending excessive HTTP requests (HTTP GET floods), holding connections open with incomplete requests (slow loris attacks), flooding the server with POST requests, manipulating TLS connections, and overwhelming it with DNS queries.
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Protocol attacks
Protocol attacks typically target layers 3 and 4 of the OSI model, focusing on network devices like routers. It target weaknesses in the basic communication systems that power the Internet, such as the TCP/IP protocol. These attacks focus on overloading the network’s ability to manage traffic.
For example, SYN flood attacks flood the target with an overwhelming number of TCP SYN packets, making it impossible for the system to handle legitimate connections. These attacks are also known as “computational” attacks because they put excessive strain on devices like routers and firewalls, causing them to struggle with handling the traffic.
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Volumetric attacks
Volumetric attacks are some of the most common types of DDoS attacks. These attacks focus on overwhelming the target’s network by flooding it with enormous data or traffic. Examples include UDP floods, ICMP floods, and reflection attacks that use protocols like NTP, Memcached, and DNS to increase traffic hitting the target.
The sheer volume of traffic can cause the target’s network unavailable to real users. These attacks typically target different layers of the network (layers 3, 4, or 7), with SYN floods being a popular type that can overload firewalls and other key network systems.
How to Prevent DDoS Attacks?
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Blackhole Routing
One common solution for network administrators is to use blackhole routing, which directs all incoming traffic into a “blackhole” and drops it from the network. In its simplest form, blackhole filtering doesn’t differentiate between legitimate and malicious traffic—it just sends everything to the blackhole.
If a website is under a DDoS attack, the site’s Internet service provider (ISP) may route all traffic to a black hole as a protective measure. However, this isn’t an ideal solution, as it makes the site completely inaccessible, which is exactly what the attacker wants.
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Rate Limiting
Rate limiting involves restricting the number of requests a server will accept within a specific period, which can help protect against denial-of-service (DoS) attacks.
While rate limiting helps slow web scrapers and prevent brute-force login attempts, it may not be enough to entirely stop a complex DDoS attack.
However, when combined with other strategies, rate limiting can be valuable to a strong DDoS defense plan.
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Web Application Firewall (WAF)
A Web Application Firewall (WAF) helps protect against Layer 7 DDoS attacks by acting as a barrier between the internet and your server. It works like a reverse proxy, filtering out harmful traffic before it reaches your server.
The WAF filters requests using rules that identify traffic from DDoS tools, helping to stop Layer 7 attacks. One of the key benefits of a good WAF is the ability to quickly create custom rules to respond to ongoing attacks.
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Anycast Network Diffusion
Anycast network diffusion helps spread DDoS attack traffic across multiple distributed servers, making it easier to manage. Think of it like diverting a rushing river into several smaller channels, reducing the impact of the attack and making it more manageable.
The effectiveness of this approach depends on both the size of the DDoS attack and the strength of the Anycast network.
For example:
CDNs play a key role in protecting against DDoS attacks by spreading traffic across multiple servers. This helps absorb sudden traffic spikes and reduces the strain on your main server. By distributing resources globally and optimizing cached content, CDNs not only improve your website’s reliability but also enhance its overall performance.
DoS Attack vs. DDoS Attack
| Aspect | DoS Attack | DDoS Attack |
| Source of Attack | Single attacker or source | Multiple attackers or sources (botnet) |
| Traffic | Floods the target with traffic from one source | Floods the target with traffic from many sources |
| Scale | Limited in scale due to single-source attack | Large-scale attack due to multiple distributed sources |
| Complexity | Easier to mitigate as it comes from one location | Harder to mitigate as traffic comes from various locations |
| Impact | It can still cause disruption but is often less impactful than DDoS | More powerful and difficult to stop, with a higher potential for disruption |
| Detection | It is more straightforward to detect as it originates from one IP address | More challenging to detect as traffic comes from a variety of IPs |
| Mitigation | Can block the attacker’s IP address easily | Requires more advanced mitigation strategies, like traffic filtering |
| Types | Types of DOS Attacks are:
1. Buffer overflow attacks 2. Ping of Death or ICMP flood |
Types of DDOS Attacks are: 1. Volumetric Attacks 2. Protocol Attack 3. Application Layer Attacks 4. Asymmetric Attacks |
What is a Smurf DDoS Attack?
A Smurf attack occurs when an attacker sends fake ping requests to a network by spoofing the IP address of the targeted server. This tricks the networked devices into responding to the server, overwhelming it with traffic.
Since these ping requests don’t require verification, they can multiply endlessly, effectively causing the networked devices to flood the target server with responses, creating a DDoS attack against its own system.
Examples of DDoS Attacks
Here are some notable DDoS attacks that highlight the serious impact of this cyber threat and offer valuable insights for improving security defenses:
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Dyn (2016)
The 2016 Dyn cyberattack disrupted major services like Netflix and PayPal by targeting DNS provider Dyn. The attackers used the Mirai botnet to flood Dyn’s servers with 1.2 Tbps of malicious traffic. This attack exposed vulnerabilities in IoT devices and DNS infrastructure, leading to increased efforts to secure these systems.
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Cloudflare (2020)
In 2020, Cloudflare faced a massive DDoS attack that peaked at 2.3 Tbps. The attack targeted a gaming customer and involved over 600,000 devices, demonstrating the scale and complexity of modern DDoS threats.
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Amazon Web Services (2020)
AWS experienced a three-day DDoS attack in 2020 that reached 2.3 Tbps. The attackers exploited misconfigurations in CLDAP servers to amplify the attack, targeting an unidentified AWS customer. This incident highlighted the importance of securing server configurations to prevent such vulnerabilities.
Conclusion
DDoS attacks remain a significant and evolving threat to organizations of all sizes, targeting critical infrastructure and disrupting services. The scale of these attacks has grown, with attackers leveraging botnets, amplification techniques, and vulnerabilities in IoT devices to generate massive amounts of malicious traffic. As these attacks become more sophisticated, it’s crucial for businesses to adopt multi-layered defense strategies, including traffic filtering, rate limiting, and robust security infrastructure. Understanding past attacks, staying updated on security best practices, and utilizing advanced DDoS protection services can help mitigate the risk and ensure the resilience of online services against these disruptive threats.
Frequently Asked Questions
1. How Long Does a DDoS Attack Last?
The duration of a DDoS attack can vary. Some attacks, like the Ping of Death, are brief, while others, like the Slowloris attack, take longer to unfold. According to a Radware report, 33% of DDoS attacks last about an hour, 60% last less than a day, and 15% can persist for up to a month.
2. Which Industries Are Most Targeted by DDoS Attacks?
DDoS attacks can affect any industry, but they most commonly target:
- Online gaming and gambling: For competitive advantage or financial gain.
- Service providers: To steal data, disrupt services, or damage reputation.
- Cloud services (AWS, Azure, etc.): For data theft, disruption, or inflict reputational damage.
- Governments: To steal intellectual property or disrupt operations.
- Financial services: For financial gain, data theft, or reputational damage.
- Online retailers: To disrupt operations or steal intellectual property.
3. How Much Malicious Traffic Is Sent in a DDoS Attack?
DDoS attacks can generate varying amounts of traffic, ranging from a few Gbps to over 1 Tbps, depending on the attack’s size, the resources involved, and the target’s defenses.
- Small-Scale Attacks: Produce traffic of a few Gbps, typically targeting smaller businesses or low-bandwidth websites.
- Medium-Scale Attacks: Generate tens of Gbps, targeting medium-sized companies or popular sites, overwhelming less-prepared networks.
- Large-Scale Attacks: Produce hundreds of Gbps, typically targeting major services like online platforms.
- Massive Attacks: Can exceed 1 Tbps, with some surpassing this, aimed at large-scale services like cloud providers and financial institutions.
