What Are the Most Common Types of DDoS Attacks and How Do They Work?

A Distributed Denial‑of‑Service (DDoS) attack floods a target’s network or application with bogus traffic, overwhelming resources and rendering services unavailable to legitimate users. Attackers harness botnets—networks of compromised devices—to generate massive traffic volumes or exploit protocol weaknesses.

Quick Takeaways

• DDoS attacks are classified into Application, Protocol, and Volumetric categories.
• Application‑layer attacks target specific services like DNS or web servers using seemingly legitimate requests.
• Protocol attacks abuse low‑level network protocols (e.g., SYN, Ping of Death) to exhaust server resources.
• Volumetric attacks overwhelm bandwidth with massive traffic, often using amplification techniques.
• Modern attacks combine multiple types to increase impact.
• Detection is difficult; proactive monitoring and mitigation are essential.
• No industry is immune—any organization with an online presence can be targeted.

What is a DDoS attack and how does it work?

A DDoS attack floods a target with traffic from many compromised devices (a botnet). The traffic can be legitimate‑looking requests or malformed packets that consume bandwidth, CPU, or memory, preventing real users from accessing the service.

What are the three main categories of DDoS attacks?

The attacks fall into Application‑layer, Protocol, and Volumetric groups. Application attacks target specific software functions, protocol attacks abuse networking protocols, and volumetric attacks overwhelm the network’s bandwidth.

How do Application‑layer attacks disrupt services?

These attacks mimic normal user behavior to hit vulnerable services. Common sub‑types include DNS server attacks that use spoofed queries and HTTP/S encrypted floods that overwhelm web servers with massive GET/POST requests.

What is a DNS server attack?

Attackers send a flood of DNS queries—often spoofed—to overload the server. Amplification techniques can turn a small query into a large response, magnifying the traffic directed at the target.

What is an HTTP/S encrypted flood?

Botnets generate a high volume of HTTP or HTTPS requests to a web server, exhausting its connection pool and CPU. Because the traffic looks like normal web traffic, it can be hard to filter.

What are common Protocol‑level attacks?

Protocol attacks target the underlying communication mechanisms. Examples include:

• Ping of Death – oversized ICMP packets that crash or reboot systems.
• SYN Flood – a barrage of half‑open TCP connections that fills the server’s backlog.
• Tsunami SYN Flood – larger packets than a regular SYN flood, increasing impact.
• Connection Exhaustion – overwhelms firewalls, load balancers, or SSL handshakes, depleting state tables.

What is a SYN Flood and why is it effective?

Attackers send thousands of SYN packets with spoofed source IPs. The server allocates resources for each half‑open connection, eventually exhausting its capacity and denying legitimate connections.

What are Volumetric attacks and how do they differ?

Volumetric attacks focus on saturating bandwidth using massive traffic volumes, often via amplification. They are measured in gigabits or terabits per second.

What is DNS amplification?

Attackers send small spoofed DNS queries to open resolvers, which reply with large responses to the victim’s IP, inflating traffic volume dramatically.

How do UDP and ICMP floods work?

UDP floods send random packets to many ports, while ICMP (ping) floods flood the network with echo requests. Both consume bandwidth and processing power.

What is an RST‑FIN flood?

Attackers send a high rate of spoofed TCP RST or FIN packets, forcing the target to close connections repeatedly, disrupting legitimate traffic.

How can organizations detect DDoS attacks early?

Monitoring traffic spikes, unusual protocol usage, and sudden drops in performance can indicate an attack. Integrating with a service like Palisade’s Email Security Score helps gauge overall exposure.

What steps should be taken to mitigate DDoS attacks?

Implement network‑level filtering, rate limiting, and use DDoS‑mitigation services that can absorb large traffic volumes. Regularly update and patch applications to reduce exploitable vulnerabilities.

Frequently Asked Questions

• Can a small business be targeted? Yes—attackers often use inexpensive botnets to hit any internet‑facing service.
• Are DDoS attacks illegal? In most jurisdictions, launching a DDoS attack is a criminal offense.
• Do cloud providers protect against DDoS? Major providers offer built‑in DDoS protection, but additional third‑party services may be required for large attacks.
• How long do attacks typically last? They can range from minutes to weeks, depending on the attacker’s goals and resources.
• Is there a way to test my defenses? Conduct controlled stress‑testing or engage a professional DDoS simulation service.