HTTP Flood DDoS attack

Web applications are a central part of business operations for organizations of all sizes. The availability of these applications is therefore crucial, but their ubiquity also means they are repeatedly targeted by cyberthreats. One particularly malicious threat is the HTTP Flood DDoS attack, which aims to overwhelm web servers and applications with a flood of seemingly legitimate requests. 

What is an HTTP Flood DDoS attack?

An HTTP Flood DDoS attack is a specific type of layer-7 DDoS attack that is distinguished by its sophisticated nature. Instead of exhausting a server’s bandwidth with raw data, an HTTP Flood attack aims to exhaust the server’s resources by overwhelming it with an enormous number of HTTP requests that appear completely legitimate at first glance.

These requests are designed to bypass typical security mechanisms because they can contain valid HTTP headers and parameters. This makes it difficult for the server to distinguish between legitimate users and malicious attackers. You can think of it as an army of cold callers all knocking on your door at the same time, pretending to be legitimate visitors. 

How does an HTTP Flood DDoS attack work?

To fully understand the threat of HTTP Flood attacks, it is important to consider how they work in detail. The attack usually begins with an attacker taking control of a botnet – a network of compromised computers or devices that can be controlled remotely without their owners’ knowledge. This botnet serves as the starting point for the actual cyberattack, and the bots are instructed to send a massive number of HTTP requests to the targeted server.

These requests can take various forms, such as HTTP GET requests to retrieve data or HTTP POST requests to send information to the server. The server, which is typically designed to handle a certain number of requests at a time, is unable to handle the flood of requests. This causes it to overload, resulting in degraded performance or complete failure. In some cases, attackers use sophisticated techniques such as slowloris, in which they send a large number of HTTP requests that are intentionally slow and incomplete, to keep the server’s connections open and prevent it from processing legitimate requests. 

Targets of HTTP Flood DDoS Attacks

In theory, any website or web application can be the victim of an HTTP Flood DDoS attack. In practice, however, certain types of organizations are particularly vulnerable and therefore more likely to be targeted. These include: 

• E-commerce sites: An attack on an e-commerce site can result in lost revenue and reputational damage, especially during key sales periods. 

• Financial services: Attacks on banks or other financial institutions can disrupt access to critical services and undermine customer trust. 

• Media organizations: News websites and other media organizations are vulnerable to attacks that seek to prevent the dissemination of information. 

• Government agencies: Attacks on government websites can deny citizens access to important services and affect public perception. 

Identifying periods of risk for HTTP Flood DDoS attacks

HTTP Flood DDoS attacks can occur at any time, but there are certain times when the risk is increased. These include: 

• Busy times: During peak periods, such as major sales promotions or important news events, an attack is more likely to be successful because the server is already very busy. 

• Political or social unrest: Organizations that take a controversial position on a political or social issue may be targeted by activists or other groups. 

• After security vulnerabilities are disclosed: Immediately after a security vulnerability in a web application is disclosed, attackers may try to exploit it before the organization has time to fix it. 

Motives behind the attacks

The motives behind HTTP Flood DDoS attacks can be varied. In some cases, they are purely acts of vandalism, designed to cause chaos and disrupt operations. In other cases, the attackers may be politically or ideologically motivated, seeking to punish organizations they view as adversaries. And finally, some attacks may be financially motivated, with attackers demanding a ransom to stop the attack or attempting to harm competitors. 

Strategies and technologies for protection against HTTP Flood DDoS attacks

Protecting against HTTP Flood DDoS attacks requires a multilayered approach of both preventive measures and reactive techniques. Key strategies include: 

• Web application firewall (WAF): A WAF is a firewall designed specifically to protect web applications. It can detect and block malicious HTTP requests before they reach the server by analyzing HTTP traffic and recognizing patterns that indicate attacks. 

• Rate limiting: By limiting the number of requests that a user or IP address can send in a given period of time, you can prevent a single attacker from overloading the server. 

• Challenge-response systems (e.g., CAPTCHAs): Using challenge-response systems, such as CAPTCHAs, can help ensure that requests are coming from legitimate users and not bots. 

• Content Delivery Network (CDN): A CDN can help distribute traffic and reduce the load on the server by storing copies of website content on servers around the world. 

• DDoS protection solutions: There are a number of specialized DDoS protection solutions that use a variety of mitigation techniques to detect and mitigate attacks. These services can be a valuable addition to a company’s internal security measures. 

• Behavioral analysis: By monitoring traffic and identifying unusual patterns that could indicate an attack, organizations can take early action to mitigate any risk. 

Additional mitigation techniques for experts

• IP reputation: Evaluating the reputation of IP addresses can help identify malicious sources and block or throttle traffic from those sources. 

• JavaScript challenges: Embedding JavaScript code in the website can be used to check whether the client is a real browser and not an automated bot. 

• Cookie-based defense: Setting cookies can be used to identify legitimate users and distinguish them from bots. 

Monitoring and analysis: The basis for effective defense

Effective protection against HTTP Flood DDoS attacks requires continuous monitoring and detailed analysis of web server traffic. This includes real-time monitoring for suspicious activity as well as evaluation of web server log files to identify attack patterns. By detecting attacks early, companies can respond quickly and minimize damage. 

Expert support in an emergency

For many organizations, it makes sense to work with specialized DDoS protection providers. These providers have the comprehensive infrastructure and expertise to effectively mitigate DDoS attacks. There are various models for collaboration, from fully outsourcing DDoS protection to hybrid solutions that combine internal security measures with external DDoS protection services. 

HTTP Flood DDoS attacks pose a serious threat to web applications and can have a significant impact on business operations. Organizations need to be aware of this type of threat and take proactive measures to protect their web resources. By implementing a multi-layered approach that includes preventive measures, reactive techniques, continuous monitoring, and working with DDoS protection providers, organizations can significantly reduce the risk of HTTP Flood DDoS attacks and ensure the availability of their web applications. 

Do you have questions about an effective defense against such attacks? Our experts will be happy to help you at any time.

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