What Is a DDoS Attack?

A Distributed Denial of Service (DDoS) attack is a malicious attempt to disrupt the regular traffic of a targeted server, service, or network by overwhelming the target or its surrounding infrastructure with a flood of internet traffic. Multiple compromised computer systems execute DDoS attacks, often called botnets, which the attacker controls.

Here’s a step-by-step breakdown of how these attacks typically work:

1. Botnet formation: The attacker first infects numerous internet-connected devices with malware, creating a botnet. These devices could be computers, mobile phones, or Internet of Things (IoT) gadgets like smart fridges, air quality monitors, and locks. The infected devices, under the attacker's control, are programmed to send massive requests to the target.
2. Command and control: Next, the attacker uses a command-and-control (C&C) server to coordinate the botnet. Through the C&C server, the attacker instructs the botnet to begin the attack, specifying the target, timing, and the type of traffic to send.
3. Traffic flooding: Once activated, the botnet sends a traffic flood to the target. Depending on the type of DDoS attack, this traffic could be in the form of data packets, HTTP requests, or even complex application-layer requests. The target’s resources—like bandwidth, CPU, and memory—become overwhelmed.
4. Denial of service: As the target's system struggles to cope with the overwhelming traffic, legitimate users need help accessing the service. The duration of the attack can vary, but the result is a significant disruption to the target’s operations.

Early identification of a DDoS attack is crucial to mitigating its effects. While some symptoms may be similar to other network issues, there are specific indicators that suggest a DDoS attack is occurring:

• Unusual traffic patterns
• Sluggish network performance
• Inaccessible services
• Increased number of requests to a single endpoint
• Unusual geographic distribution of traffic
• Alerts from security tools

Denial of Service (DoS) attacks aim to disrupt a service or network by overwhelming it with excessive traffic. The main difference between a DoS and a DDoS attack lies in the scale and origin of the attack.

A DoS attack is launched from a single source, making it easier to detect and mitigate, often by blocking the offending IP address. In contrast, a DDoS attack is executed from multiple sources simultaneously, using a botnet of compromised devices spread across various locations. This distributed nature makes DDoS attacks more potent and challenging to defend against, as the traffic comes from numerous IP addresses, making it difficult to distinguish between legitimate and malicious traffic.

The scale of a DDoS attack is significantly greater than that of a DoS attack. While a DoS attack can still cause disruption, particularly for targets with limited resources, a DDoS attack can generate overwhelming traffic, taking down even large, well-resourced organizations. The complexity of defending against a DDoS attack is also much higher, often requiring advanced mitigation techniques and specialized DDoS protection services to absorb and filter out the malicious traffic without affecting legitimate users.

DDoS attacks can be categorized into three main types based on the method they use to overwhelm their target:

1. Volume-Based Attacks: These attacks aim to saturate the bandwidth of the target site by sending massive amounts of data. The primary goal of volume-based attacks is to overwhelm the network infrastructure, making it impossible for legitimate traffic to reach the target and effectively causing a denial of service. Examples include User Datagram Protocol (UDP) and Internet Control Message Protocol (ICMP) floods.
2. Protocol Attacks: These attacks focus on exhausting server resources by exploiting weaknesses in the protocols used for communication between servers. Examples include Synchronize (SYN) floods and fragmented packet attacks. By targeting the protocol layer, these attacks can consume server resources, such as processing power and memory, leading to server crashes or unavailability.
3. Application Layer Attacks: These are the most sophisticated DDoS attacks, targeting the layer where web pages are generated on the server and delivered to the user. These attacks are hazardous because they mimic legitimate user behavior, making them harder to detect and mitigate while causing significant disruption to the application’s functionality. Examples include Hypertext Transfer Protocol (HTTP) floods and Domain Name System (DNS) query attacks.

Given the complexity and scale of DDoS attacks, a multi-layered defense approach is essential to mitigate the impact and restore normal operations. Here’s how to effectively stop a DDoS attack:

1. Activate DDoS protection services: Use specialized DDoS protection services, like SolarWinds^® Security Event Manager, to filter and absorb malicious traffic before it reaches your network.
2. Implement traffic filtering and rate limiting: Deploy traffic filtering to block malicious requests and apply rate limiting to control the number of requests a user can make, reducing the attack's impact.
3. Use a Content Delivery Network (CDN): A CDN distributes content across multiple servers globally, absorbing attack traffic and maintaining service availability even if one server is targeted.
4. Monitor traffic in real-time: Use real-time monitoring tools to detect unusual traffic patterns or spikes, allowing you to respond quickly to the attack.
5. Contact your ISP: Contact your Internet Service Provider (ISP) for additional support. ISPs can filter out attack traffic at their level, reducing the load on your network.
6. Isolate affected systems: If the attack is focused on specific areas, isolate those systems to contain the impact and prevent the attack from spreading.
7. Conduct post-attack analysis: After stopping the attack, analyze the incident to identify vulnerabilities and improve your defenses for future attacks.

Preventing DDoS attacks requires a proactive approach, but it remains challenging due to their complexity and scale. DDoS attacks are brutal to control due to their scale, distributed nature, and the constant evolution of attack methods. The sheer volume of traffic from multiple sources makes distinguishing between legitimate and malicious activity hard. However, there are some strategies to help prevent such attacks:

• Multi-layered defense: Use a combination of firewalls, intrusion detection systems (IDS), and intrusion prevention systems (IPS) to filter out malicious traffic.
• DDoS protection services: Employ services like SolarWinds Security Event Manager to detect and mitigate attacks before they impact your network.
• Content Delivery Network (CDN): Distribute content across multiple servers to minimize the impact of an attack on any single server.
• Rate limiting: Control the number of requests per user to prevent your system from being overwhelmed.
• Regular audits and updates: Conduct security audits and keep your systems up-to-date to reduce vulnerabilities.