1. What is DDoS?
DDoS (Distributed Denial of Service) is a denial-of-service attack in which attackers leverage multiple compromised devices, such as computers, servers, and IoT devices within a botnet—to flood the target system with a massive volume of illegitimate traffic simultaneously. The goal is to exhaust server resources, rendering websites or applications unable to respond to legitimate user requests.
Unlike traditional DoS attacks, which originate from a single source, DDoS operates in a distributed manner, sourcing traffic from numerous IP addresses across diverse geographic locations. This makes detection and mitigation significantly more challenging, especially for servers lacking advanced security measures. In simple terms, when the system is forced to process far more requests than it can handle, the server becomes overloaded, slows down dramatically, or shuts down completely.
2. Why are DDoS attacks so dangerous?
DDoS ranks among the most threatening denial-of-service attack types today, due to its scale, ease of execution, and the severe business impact it delivers.
2.1 Low cost and ease of execution
Previously, launching a DDoS attack required advanced technical knowledge and complex infrastructure. Today, however, the rise of DDoS-for-hire services has made this attack method more accessible than ever.
According to VNETWORK's 2026 Vietnam Cyberattack Report, the system recorded over 512,438 DDoS attacks, accounting for 18.7% of all recorded events, with peak intensity reaching 1.89 Tbps. This figure increased by 87,000 incidents compared to the same period in 2024 (a 51% increase), averaging 42,700 attacks per month. With minimal cost, attackers can rent a botnet to generate massive traffic, enough to overload the DDoS servers of many small and medium businesses.
2.2 Significant financial losses
The most obvious consequence of DDoS is service disruption. When a website or application cannot operate normally, the business loses revenue directly, while also incurring costs to remediate the incident and restore the system.
Frequent service disruptions also erode brand reputation and customer trust, particularly in sectors such as e-commerce during peak sales periods, banking and finance, and other online services.
2.3 Difficult to detect and prevent in time
Unlike conventional cyberattacks, today's DDoS attacks are typically carried out through botnets involving a large number of devices, using spoofed IP addresses and multiple attack methods simultaneously.
With the support of AI, DDoS attacks can now be dynamically adjusted, mimicking real user behavior and automatically altering traffic patterns. VNETWORK's system recorded that nearly 50% of all DDoS attacks in Vietnam (equivalent to more than 117,000 attacks) involved AI. This makes malicious traffic increasingly difficult to distinguish from legitimate traffic.
2.4 A stepping stone for larger attacks
In many cases, a DDoS attack is not the attacker's final goal but serves as a diversion. While a system is overwhelmed by DDoS traffic, attackers may exploit this window to exploit security vulnerabilities, gain unauthorized access to data, or deploy ransomware. This makes DDoS a threat not only to service continuity but to a business's overall information security.
3. How do DDoS attacks work?
To understand why a DDoS attack can bring a system down within a short period, businesses need to understand the basic mechanics behind this type of denial-of-service attack. Below is a typical DDoS attack process:
- Building a botnet: The attacker first gains control of a large number of Internet-connected devices, such as computers, servers, or IoT devices, through malware, turning them into "malicious bots" operating under remote control. This forms the foundation for launching large-scale DDoS attacks.
- Centralized control: Through a centralized control system, the attacker commands the entire botnet to target a specific IP address or system simultaneously. Because of its distributed nature, traffic in a denial-of-service attack can originate from many countries and IP ranges.
- Sending massive traffic to the target: Each bot continuously sends connection requests or data packets to the targeted system, generating an abnormally large volume of traffic. Once the number of bots is large enough, the DDoS server has to handle traffic far exceeding its normal processing capacity.
- Exhausting system resources: While processing invalid requests, server resources such as bandwidth, CPU, or connection buffers are quickly consumed. This leaves the system without enough capacity to respond to legitimate requests from real users.
- Denying service to legitimate users: Once resources are overloaded, the website or application becomes slow, error-prone, or completely inaccessible. The end result of DDoS is service disruption, directly affecting user experience and business operations.
4. How to recognize a DDoS attack
By observing unusual changes in traffic, response times, and system behavior, businesses can detect early signs of this type of attack:
- Slow or inaccessible website: When resources are overloaded by a DDoS attack, the website or application becomes slow, error-prone, or completely inaccessible, even when the underlying infrastructure remains stable.
- Abnormal traffic patterns: Traffic spikes suddenly, originating from many unfamiliar IP addresses, triggering alerts in network monitoring tools.
- Repeated access requests: Continuous requests following the same pattern or targeting sensitive endpoints are a sign that the system is under attack.
- Server errors and failed connections: Recurring server errors, timeouts, or abruptly reset connections are clear signals of a denial-of-service attack.
- System resource overload: When bandwidth, CPU, or connection buffers are fully consumed, the system can no longer serve legitimate users, causing service disruption.
5. Common types of DDoS attacks
5.1 Volumetric DDoS Attacks
This group of attacks mainly targets the lower layers of the OSI model, such as layer 3/4, where network traffic is processed. The goal is not to break the application itself but to flood the network path, affecting every service running above it.
- UDP Flood: At the network protocol layer, the system must receive and process a large number of invalid data packets. Although each packet is harmless on its own, the cumulative effect quickly drains bandwidth and processing resources, preventing real users from accessing the service.
- ICMP Flood (Ping Flood): This attack targets the processing of control packets within the network. As the server continuously responds to ping requests, network-layer resources become consumed, leading to congestion across the entire system.
- NTP/DNS Amplification: Instead of sending large volumes of data directly, attackers exploit intermediary servers to amplify traffic. This creates enormous pressure on the DDoS server at the network infrastructure layer, causing overload within a very short time.
5.2 Protocol DDoS Attacks
Protocol Attacks do not aim to generate large volumes of traffic but instead focus on exhausting the processing resources inside the system. They exploit how the server manages connections, memory, and processing queues, destabilizing the system even when bandwidth is not yet congested.
- SYN Flood: The server is forced to maintain a large number of half-open connection states, consuming memory and resources meant for legitimate connections. Once the number of pending connections reaches a threshold, real users can no longer establish new sessions.
- Ping of Death: The system is forced to process abnormal data packets, which can cause errors during packet analysis. On infrastructure that has not been fully updated, this can easily lead to system freezes or forced service restarts.
- IP Null/Fragment Flood: Incomplete or fragmented data packets force the server to spend significant resources reconstructing them. When this process occurs continuously, overall performance drops sharply, creating a high risk of widespread disruption.
5.3 Application DDoS Attacks
This group of attacks targets the application layer, Layer 7 directly, where websites, APIs, and digital services operate. What makes this dangerous is that the requests closely resemble genuine user behavior, making it difficult for security systems to distinguish legitimate traffic from a denial-of-service attack.
- HTTP Flood: At the application layer, the server has to process a massive number of seemingly valid requests. Processing resources are gradually consumed, keeping the website "online" but causing noticeably slower response times and a degraded user experience.
- Slowloris: Connections are kept open for extended periods at the application layer, leaving the server without enough resources for new sessions. This is a sophisticated form of attack because it doesn't require large volumes of traffic to cause congestion.
- Misused Application Attack: Legitimate functions such as search, login, form submission, or API calls are exploited excessively, forcing the application layer to handle workloads beyond its original design and destabilizing the entire service.
5.4 Zero Day DDoS
Zero Day DDoS is an especially dangerous form of attack because it exploits vulnerabilities that are unknown or not yet patched. This type of attack can affect anything from network infrastructure (bandwidth, routers) to the application layer (websites, APIs, servers), meaning every layer of the system is at risk. The most concerning aspect is that when it occurs, businesses have almost no ready defense and must spend time identifying the source and implementing a fix. As a result, Zero Day attacks often lead to prolonged service disruption and significant financial damage.
Explore the top DDoS protection services suited to different business sizes: Here
6. Industries most targeted by DDoS attacks
According to VNETWORK's cybersecurity report, the level of risk from DDoS attacks varies significantly across industries:
- Finance and banking rank highest at 34.7%. This sector requires systems to operate continuously and process transactions in real time, so even a brief disruption can cause financial losses and undermine customer trust.
- Manufacturing, retail, and e-commerce account for 23.9%. Websites serve as the primary sales and order-processing channel, so service disruptions during peak periods can lead to significant revenue loss.
- Publishing and media account for 19.5%. High and fluctuating traffic volumes make content platforms an easy target for exploitation.
- Education accounts for 10.7%. The rapid growth of online learning and digital testing has outpaced security investment in many institutions.
- Travel accounts for 8%. Booking and ticketing systems face heavy pressure during peak periods, which is also when they are most likely to be targeted.
- Other industries account for the remaining 3.2%, showing that DDoS is not limited to any single sector and can affect any online system.
Overall, industries that rely heavily on online systems to operate and generate revenue face a higher risk of DDoS attacks and should prioritize investment in appropriate protection solutions.
7. Simulated DDoS attack guide
A DDoS attack on a website or application doesn't just harm the business, it also disrupts the customer experience. While a website is under DDoS attack, customers are unable to access it or complete the transactions they intend to make. Today, many free tools are available that let you simulate a DDoS attack to better understand how dangerous this type of distributed denial-of-service attack can be.
To simulate a DDoS attack, we'll use LOIC (Low Orbit Ion Cannon), developed by Praetox Technology and famously used by the hacker group Anonymous to carry out DDoS attacks over the years.
Steps to carry out a simulated DDoS attack with LOIC:
7.1 Step 1 - Download LOIC
You can download LOIC from SourceForge. Next, you'll need to disable your antivirus warning and extract the zip file after downloading it successfully.
7.2 Step 2 - Launch LOIC and start the DDoS attack
After running LOIC, a menu will appear allowing you to configure the tool. There are several options you can set, such as choosing the target IP or URL, configuring the port, the number of threads, and the attack speed.
7.3 Step 3 - Confirm
Once configuration is complete, simply click "IMMA CHARGIN MAH LAZER" to launch the attack and observe how it unfolds.
After testing the attack simulation, the attacked website will consume a large number of resources because it has to process all requests from the large amount of invalid traffic generated by the DDoS.
To overcome the situation of attacks that disrupt access as well as minimize the damage caused by cybercriminals to businesses, let’s work with VNETWORK to learn and choose effective anti - DDoS tools.
8. How to prevent DDoS attacks
Below are some common DDoS prevention methods that businesses and organizations typically use to protect their systems against increasingly sophisticated attacks.
8.1 Expand bandwidth and use a CDN
One of the simplest yet effective ways to reduce the impact of a denial-of-service attack is to increase the system's capacity to handle load. With sufficient bandwidth, high-volume attacks become much harder to overwhelm the entire service.
Combining this with a CDN (Content Delivery Network) helps distribute traffic across multiple points instead of concentrating it on a single server. As a result, even during a DDoS attack, the website can maintain stable access for real users.
8.2 Use a WAF (Web Application Firewall)
WAF acts as a protective layer in front of websites and applications. It helps control incoming requests, detecting and blocking abnormal behavior before it penetrates deeper into the system.
Especially for application-layer DDoS attacks, WAF reduces processing pressure on the server by filtering out unnecessary requests or those showing signs of function abuse.
8.3 Rate limiting
Rate limiting controls the number of requests a user or IP address can send within a given time period. This is particularly effective at preventing rapid-fire requests designed to overload the system.
By limiting access speed, the DDoS server can prioritize serving real users while reducing the risk of functions such as login, search, or API calls being exploited.
8.4 Continuous monitoring and early detection
Finally, continuous system monitoring is a key factor in DDoS prevention. When a business can track traffic and performance in real time, unusual signs can be detected earlier.
Early detection allows technical teams to respond proactively before an attack escalates to the point of causing serious disruption, reducing the impact on revenue and user experience.
9. VNIS - Comprehensive DDoS protection solution
VNETWORK is a technology company with more than 13 years of experience in security and network infrastructure, currently partnering with over 200 leading businesses in Vietnam, including MoMo, Vietcap, HSC, ACBS, Coolmate, FireAnt, VieOn, and VOV. Drawing on real-world experience managing high-traffic systems, VNETWORK developed VNIS, a solution that helps businesses proactively address large-scale DDoS risks.
VNIS is VNETWORK's security and acceleration solution for Web/App/API, protecting against multi-layer DDoS attacks (Layer 3/4/7), malicious bots, and vulnerability exploits such as SQL Injection, XSS, zero-day, malware, and dangerous crawlers in real time. With AI capabilities, abnormal behavior is detected and blocked early, while performance and user experience remain uncompromised.
Beyond security, VNIS also maintains speed and stability for websites and applications even under high traffic conditions. The solution runs on a global infrastructure with over 2,300 PoPs across more than 146 countries, capable of handling up to 2,600 Tbps of traffic and more than 10 billion requests per day. With over 2,400 active security rules, VNIS currently protects more than 400,000 websites, applications, and APIs, helping business systems stay ready for large-scale DDoS attacks.
9.1 How VNIS works
VNETWORK's VNIS solution is designed around a two-layer protection model, effectively defending against DDoS attacks at both the network and application layers.
- Layer 1: VNIS combines AI Smart Load Balancing and Multi-CDN to handle DDoS attacks at the infrastructure layer. AI automatically analyzes traffic behavior, distributes traffic intelligently, and filters out abnormal sources before they can overload the system.
- Layer 2: At this layer, VNIS deploys WAAP (Web Application and API Protection) powered by AI to prevent application-layer DDoS attacks, malicious bots, and common vulnerabilities listed in the OWASP Top 10. This layer directly protects the logic of the web/app/API, an area that is often exploited more deeply and harder to detect.
9.2 FireAnt - Protecting a trading platform through the night of an attack
FireAnt provides financial analysis tools and stock market data for tens of thousands of individual and institutional investors. For a financial platform, every minute of downtime during trading hours can cause direct losses for end users.
FireAnt faced two compounding problems: repeated DDoS attacks destabilizing the system, and poor data delivery performance during peak trading hours. When the incident struck in the middle of the night, VNETWORK responded immediately: activating VNIS's Multi-CDN infrastructure to isolate and absorb the attack traffic, while optimizing content delivery to keep the system stable through the night.
Results after deploying VNIS:
- FireAnt fully recovered on the same night the incident occurred, with no disruption carrying over to the next morning's trading session.
- The system successfully withstood sustained attacks exceeding 150 Gbps per day, continuing for months without requiring any additional infrastructure upgrades.
- Data delivery performance improved significantly during peak trading hours, where even a second of latency can directly impact investment decisions.
- FireAnt's engineering team no longer needs to respond manually to attacks. VNIS handles mitigation automatically, with VNETWORK's SOC providing continuous 24/7 monitoring.
10. Conclusion
DDoS attacks are becoming easier to launch, harder to detect, and faster to cause damage than ever before. Businesses cannot afford to wait until their systems go down before looking for a solution. By that point, the revenue loss and reputational damage have already been done.
Understanding DDoS is the first step, but what businesses truly need is a layer of protection that is ready before an attack ever hits. VNETWORK's VNIS is built to meet exactly that need: real-time proactive defense, automated mitigation from the network layer to the application layer, ensuring no disruption ever reaches end users.
Is your business ready for the next DDoS attack?
Contact VNETWORK for a free consultation tailored to your system's scale and requirements.
- 24/7 Support Hotline: +84 (028) 7306 8789
- Email: contact@vnetwork.vn
- Learn more & start your free trial: Here
11. FAQ – Frequently asked questions about DDoS attacks
1. What is a DDoS attack?
A Distributed Denial of Service (DDoS) attack overwhelms a system with massive illegitimate traffic, preventing it from serving legitimate users.
2. Who do DDoS attacks typically target?
Any internet-connected system can be targeted, especially enterprise websites, e-commerce platforms, financial applications, online gaming, and APIs.
3. Does DDoS cause data loss?
DDoS primarily disrupts service availability, but attackers often use it as cover to execute deeper breaches, such as data exfiltration or malware deployment.
4. Is launching a DDoS attack easy?
Yes, thanks to DDoS-for-hire services and accessible botnets, even non-expert attackers can cause substantial damage today.
5. Are CDN and WAF sufficient to stop DDoS?
They significantly reduce risk, but large-scale, multi-vector, or sophisticated application-layer attacks require specialized, comprehensive solutions.
6. How does VNIS differ from standard DDoS protection?
VNIS integrates Multi-CDN, AI Smart Load Balancing, and WAAP for end-to-end defense from network infrastructure to application logic, while maintaining high performance.
7. Does VNIS slow down websites or applications?
No, VNIS is engineered for both security and acceleration, ensuring stability and speed even under elevated traffic or during active attacks.
8. Do small businesses need DDoS protection?
Yes, smaller organizations are frequent targets due to limited defenses, and even brief DDoS incidents can cause serious operational disruption.