A Protocol DDoS attack is a type of distributed denial of service (DDoS) attack that targets the rules of how devices talk to each other on the internet. Instead of using massive amounts of data, attackers send packets that are fake, broken, or incomplete. These confuse the target system and force it to waste time and power. This malicious traffic slows down or blocks legitimate traffic from getting through.
Protocol DDoS attacks focus on the lower layers of the network, such as routers, firewalls, and operating systems. Because they take advantage of how these systems handle connections, they don’t always need a huge number of requests. A well-planned protocol attack can cause serious problems even with less traffic than a big volumetric attack.
Attackers often use botnets made from IoT devices like cameras or routers. These devices are often poorly protected and always online, which makes them easy to control. When combined, they can launch strong flooding attacks that are hard to stop.
Like other denial-of-service attacks, the goal is to make a service unavailable to legitimate users. Whether the target is a business, a public service, or a gaming site, the result is usually downtime, lost income, and damage to reputation.
| Type of DDoS Attack | How the Attack Works | Key Attack Vectors and Examples | Impact on Legitimate Users |
|---|---|---|---|
| Volumetric Attack | Uses sheer bandwidth saturation to overwhelm the victim with a flood of attack traffic. Amplification methods turn small queries into huge responses. | Flooding attacks such as UDP floods, DNS amplification, and NTP amplification. Often powered by botnets of IoT devices, sending millions of packets. | Internet pipes clog with malicious traffic, leaving no space for legitimate traffic. Websites slow down or become unreachable. |
| Protocol DDoS Attack | Protocol attacks exploit the way devices handle connections and packets. Instead of only raw volume, they drain CPU, memory, and network resources with malformed or incomplete requests. | DDoS examples include SYN flood, Ping of Death, ICMP flood, and Fraggle attack. Each one manipulates low level communication rules to exhaust systems. | Servers and firewalls get stuck processing fake sessions. Legitimate users experience timeouts, slow performance, or total denial of service. |
| Application Layer Attack | Targets the higher layers where websites, apps, and APIs operate. Attackers send a huge number of requests that appear normal but overload the application. | Service DoS attacks like HTTP floods, login request floods, and search query overloads. These mimic legitimate traffic, making filtering harder. | Even a small wave of malicious traffic can overwhelm web servers. Legitimate traffic is mixed with fake requests, so real users cannot access the service. |
Here are some well-known DDoS examples that show how attacks exploit protocol weaknesses. Each one highlights a different attack vector.
In this attack, the target is the TCP three-way handshake. The attacker sends a flooding attack of SYN packets but never finishes the connection. The server keeps waiting, holding resources open. Too many half-open sessions quickly exhaust memory and CPU. This is one of the oldest forms of denial of service attacks and is still common today.
Also called a ping flood, this attack overwhelms the victim with ICMP Echo Requests. The network must respond to each, which consumes bandwidth and slows all traffic. Unlike a pure volumetric attack, the attack traffic here uses a built-in system tool. A denial of service DoS with ICMP can bring routers or servers to a halt.
This classic DoS server attack uses oversized ping packets. The packets break the rules of the IP protocol. When the target tries to process them, it can freeze or crash. While patches fix most systems today, this protocol attack shows how dangerous malformed packets can be.
Similar to a Smurf attack, but instead of ICMP, it uses UDP echo requests. Attackers send traffic to broadcast addresses. Each device in the broadcast domain responds to the victim, multiplying the number of requests. This is an early denial of service DDoS style that shows the power of amplification.
Attackers abuse public Network Time Protocol servers. They send small queries with a fake return address. The server replies with a much larger response to the victim. A few bytes in can become hundreds out. This type of service DoS attack is highly effective because the attack traffic is amplified.
Like NTP amplification, but using open DNS resolvers. A simple query for a large record returns a huge response. Again, the response goes to the victim. This can create a DDoS attack example where one attacker generates gigabits of malicious traffic with little effort.
These examples show how dangerous protocol DDoS attacks can be. With just a few commands, attackers can paralyze critical services. For businesses, the result is often downtime, financial loss, and lasting damage to reputation.
Stopping a protocol DDoS attack requires both preparation and quick action. A single tool is not enough. Here are some proven steps.
Each of these measures helps reduce the impact of protocol DDoS attacks. When combined, they create a strong, multi-layered defense that keeps services available for legitimate users.
CDNetworks gives strong protection against protocol DDoS attacks at both the network and transport layers. The platform blocks malicious traffic that abuses protocol rules, such as SYN floods, ICMP floods, and other flooding attacks. This keeps servers safe from incomplete or broken requests, while legitimate traffic can pass without delay.
The backbone of this defense is a global network with more than 2,800 Points of Presence (PoP). Incoming attack traffic is spread across many regions, so no single server is overloaded, even during large-scale DDoS attacks.
Key highlights:
By combining scale, filtering, and round-the-clock support, CDNetworks helps businesses stay online and reliable, even under heavy and complex protocol DDoS attacks.