A Flood Attack is one of the most widely used tactics in Distributed Denial-of-Service (DDoS) campaigns, allowing attackers to overwhelm networks, servers, and online services with excessive traffic. In this article, we’ll explore what a this attack is, how it works, and the top 5 most common methods.
What Flood Attack Is
A Flood Attack is a type of DDoS attack in which a target is bombarded with an enormous volume of unwanted traffic. The goal is simple: exhaust the target’s resources so legitimate users can no longer access the service. Flood attacks can overwhelm bandwidth, CPU power, memory, or application-level processes.
These attacks can be launched using botnets, spoofed IPs, or compromised devices. Because critical services such as DNS and web servers handle large amounts of requests by design, they are especially vulnerable if not properly protected.
Top 5 Flood Attack Types
SYN Flood Attack
A SYN Flood Attack targets the TCP handshake process. Attackers send numerous SYN packets without completing the handshake, causing the server to accumulate half-open connections. This quickly drains resources and disrupts legitimate traffic.
UDP Flood Attack
A UDP Flood Attack sends massive amounts of UDP packets to random ports. The target must respond with ICMP “Destination Unreachable” messages, consuming both bandwidth and CPU power. DNS servers are frequent victims due to their reliance on UDP for most queries.
ICMP Flood Attack (Ping Flood)
An ICMP Flood Attack overwhelms a target with ICMP Echo Requests. The system attempts to answer each packet with an Echo Reply, clogging bandwidth and slowing down network performance. When unfiltered, ICMP floods can easily render a network unreachable.
HTTP Flood Attack
The HTTP Flood Attack targets the application layer by sending massive numbers of HTTP GET or POST requests. These requests appear legitimate, making detection difficult. With enough volume often generated through botnets, the targeted web server becomes overloaded and crashes or becomes unresponsive.
DNS Flood Attack
A DNS Flood Attack sends huge volumes of DNS queries toward a DNS resolver or authoritative server. Randomized subdomain queries are often used to bypass caching. When DNS servers fail, websites, applications, and online services become unreachable altogether, making this one of the most disruptive types of flood attacks.
How to Protect Against Flood Attacks
Flood attacks are powerful, but several strategies can help mitigate them:
- Rate limiting to control excessive traffic
- Anycast DNS networks to distribute load
- Firewalls and packet filtering to block malicious patterns
- DDoS mitigation services that absorb large-scale attacks
- DNS-specific protection, such as response rate limiting (RRL)
Combining these methods creates multiple layers of defense, significantly reducing the risk of downtime.
Conclusion
Flood Attacks remain one of the most common and dangerous DDoS methods due to their simplicity and effectiveness. By understanding each flood attack type, SYN, UDP, ICMP, HTTP, and DNS, you can better identify vulnerabilities and strengthen your defenses. With proper preparation, strong DNS infrastructure, and advanced filtering in place, organizations can stay resilient against even the most aggressive attack waves.
