DDoS attack

A distributed denial-of-service (DDoS) attack is a malicious effort to disrupt the regular flow of traffic to a specific server, service, or network. This disruption occurs by inundating the target and its surrounding infrastructure with an excessive volume of Internet traffic. DDoS attacks are successful by employing numerous compromised computer systems as sources of attack traffic, which may include both computers and other networked resources such as IoT devices. In essence, a DDoS attack is comparable to an unforeseen traffic jam obstructing the highway, impeding regular traffic from reaching its intended destination.

How does a DDoS attack work?

DDoS attacks are executed through networks of Internet-connected machines. These networks comprise computers and various devices, including IoT devices, that have been compromised by malware, enabling remote control by an attacker. These individual devices are termed bots (or zombies), and collectively, they form a botnet.

Once a botnet is established, the attacker can orchestrate an attack by remotely instructing each bot. When targeting a victim’s server or network, each bot within the botnet sends requests to the target’s IP address. This influx of requests has the potential to overwhelm the server or network, leading to a denial-of-service for regular traffic.

The challenge lies in distinguishing the attack traffic from normal traffic, as each bot functions as a legitimate Internet device.

How to identify a DDoS attack

Identifying a DDoS attack often involves observing a sudden slowdown or unavailability of a site or service. However, as various factors like a legitimate traffic surge can cause similar performance issues, a more in-depth investigation becomes necessary. Utilizing traffic analytics tools can aid in recognizing key indicators of a DDoS attack:

1. Unusual volumes of traffic originating from a single IP address or IP range.
2. Inundation of traffic from users sharing a common behavioral profile, such as device type, geolocation, or web browser version.
3. Unexplained spikes in requests directed at a specific page or endpoint.
4. Aberrant traffic patterns, including spikes during unusual hours or patterns that seem unnatural (e.g., regular spikes every 10 minutes).

Additional, more specific signs of a DDoS attack may manifest, varying based on the specific type of attack employed.

What are some common types of DDoS attacks?

Identifying a DDoS attack often involves observing a sudden slowdown or unavailability of a site or service. However, as various factors like a legitimate traffic surge can cause similar performance issues, a more in-depth investigation becomes necessary. Utilizing traffic analytics tools can aid in recognizing key indicators of a DDoS attack:

1. Unusual volumes of traffic originating from a single IP address or IP range.
2. Inundation of traffic from users sharing a common behavioral profile, such as device type, geolocation, or web browser version.
3. Unexplained spikes in requests directed at a specific page or endpoint.
4. Aberrant traffic patterns, including spikes during unusual hours or patterns that seem unnatural (e.g., regular spikes every 10 minutes).

Additional, more specific signs of a DDoS attack may manifest, varying based on the specific type of attack employed.

Although the primary objective of nearly all DDoS attacks is to inundate a target device or network with traffic, these attacks can be categorized into three main types. An attacker may employ one or more distinct attack vectors or alternate between attack vectors in response to countermeasures implemented by the target.

Application layer attacks
The goal of the attack:

Sometimes labeled as a layer 7 DDoS attack (referring to the 7th layer of the OSI model), these attacks aim to deplete the target’s resources, causing a denial-of-service.

These attacks focus on the layer where web pages are generated on the server and delivered in response to HTTP requests. While a single HTTP request is relatively inexpensive to execute on the client side, it can be resource-intensive for the target server to respond to. This is because the server often loads multiple files and performs database queries to generate a web page.

Defending against layer 7 attacks is challenging due to the difficulty in distinguishing malicious traffic from legitimate traffic.

Example of an application layer attack:

HTTP flood:

This attack is akin to repeatedly refreshing a web browser on numerous computers simultaneously, inundating the server with a large volume of HTTP requests, leading to a denial-of-service.

The complexity of this type of attack can vary, ranging from simple to intricate.

Simple implementations may involve accessing a single URL with the same set of attacking IP addresses, referrers, and user agents. On the other hand, more complex versions may employ a multitude of attacking IP addresses, targeting random URLs using varied referrers and user agents.

What is the process for mitigating a DDoS attack?

The primary challenge in mitigating a DDoS attack lies in distinguishing between attack traffic and regular traffic.

For instance, if a company’s website experiences a surge in traffic due to a product release, blocking all traffic would be a mistake. However, if the traffic spike is from known attackers, it’s likely necessary to implement measures to mitigate the attack.

The difficulty arises in accurately identifying legitimate customers amid the onslaught of attack traffic.

In the contemporary Internet landscape, DDoS traffic manifests in various forms, ranging from straightforward single-source attacks to sophisticated and adaptive multi-vector attacks.

A multi-vector DDoS attack employs multiple attack pathways to overwhelm a target in different ways, potentially diverting mitigation efforts across various trajectories.

An example of a multi-vector DDoS attack is one that targets multiple layers of the protocol stack simultaneously, such as a DNS amplification (targeting layers 3/4) coupled with an HTTP flood (targeting layer 7).

Mitigating a multi-vector DDoS attack necessitates employing diverse strategies to counter different attack trajectories.

In general, the more intricate the attack, the more challenging it becomes to separate attack traffic from normal traffic. Attackers aim to blend in seamlessly, rendering mitigation efforts less effective.

Mitigation strategies that involve indiscriminately dropping or limiting traffic may inadvertently impact legitimate traffic. Moreover, attackers may modify and adapt their tactics to circumvent countermeasures. To effectively counter a sophisticated disruption attempt, a layered solution provides the greatest benefit.