Layer 7 attacks, also called application layer attacks, are a form of distributed denial-of-service (DDoS) attacks. Typical DDoS attacks include layer 7 attacks, network attacks, and reflection attacks, with each attack targeting a particular layer of an application model.
Although there are several kinds of DDoS attacks, on a fundamental level, they all share the same goal: to take down a website or server by overwhelming it with traffic until the web server crashes or becomes unresponsive to further requests.
Layer 7 DDoS attacks are typically more complex than other DDoS attacks. This is because, while layer 7 attacks work to flood networks and servers using HTTP traffic, these spikes in traffic are typically more challenging to identify than other DDoS attack forms. This makes mitigating them both more difficult and also more critical.
Layer 7 DDoS attacks specifically target the topmost layer (application layer) of the 7-layer Open Systems Communication (OSI) model. This layer is responsible for handling common request methods like GET and POST. A typical example of a layer 7 attack is sending thousands of requests per second to a webpage until the webpage becomes too overwhelmed to handle the traffic.
Layer 7 attacks occur slowly and require minimal packets/bandwidth to execute — around or less than 1Gbps. This minimal requirement makes them particularly effective and troubling to handle because the resources/bandwidth required to fight the attacks are much more significant than those needed to enable the attack.
Unlike network attacks, which are somewhat easier to spot and manage, a layer 7 attack is challenging to mitigate. This is mainly because, as mentioned earlier, the HTTP traffic of layer 7 DDoS attacks looks similar to harmless peaks in HTTP traffic. With a layer 7 DDoS attack, there’s usually the absence of intense traffic spikes, and any spike usually is confused with flash crowds — a sudden increase in traffic from legitimate users.
For example, in an HTTP flood attack, the bots providing the traffic spoof their IP addresses, making them seem like regular addresses. As a result, they are confused with legitimate traffic.
There are several reasons why malicious actors pursue layer 7 attacks, including those outlined below.
Ransom and extortion are generally the greatest motivators behind DDoS attacks. Malicious actors use layer 7 attacks to make a business’ services unavailable until a ransom is provided.
Seeking business advantage is an unethical yet common motivation for performing layer 7 attacks. Some businesses may aim to disrupt competitors’ operations to achieve greater success and profit. Layer 7 attacks can be used as a strategy to drive traffic to their own site or service.
This attack intends to cause political disruptions or express displeasure with a particular party. For example, political campaign websites and support servers can be targeted to prevent the political platform or party from gaining traction or reaching new supporters.
In some cases, attackers may use a layer 7 attack to distract security experts from their cybersecurity duties, explore possible weak points, and carry out even more serious offenses like data leaks.
Several methods can be used when performing layer 7 DDoS attacks: HTTP floods, cache bypass HTTP floods, WordPress XML-RPC floods, and Slowloris attacks.
HTTP floods are the most common layer 7 DDoS attack. They involve attackers using similar IP addresses and user agents to send multiple requests to the same webpage or server. This eats up the server resources and ultimately leads to the website crashing.
Considered the smartest layer 7 DDoS attack, this is a randomized HTTP flooding attack. Attackers use a wide range of IP addresses, often controlled by bots, to bypass the web application caching system that helps minimize the consumption of server resources.
By bypassing the application caching system, every new request forces the server to process and complete the request, thereby using up server resources and causing a crash. A popular technique involves requests for un-cacheable content or requests that consume a lot of bandwidth and cause slow response time (and downtime) for legitimate traffic.
The WordPress XML-RPC is a connection medium that helps WordPress communicate with other applications. This connection uses HTTP for transport and encodes information using XML. Pingback and backtracks are two functions enabled by the WordPress XML-RPC connection. These functions present notifications as comments on a WordPress site when other blogs link to your blog.
However, an attacker may take advantage of this connection and initiate a layer 7 DDoS attack by sending massive amounts of Pingback to your webpage, thereby overwhelming your web server and causing a crash.
Slowloris attacks are the most harmful layer 7 DDoS attacks. They’re slow and elegant, involving opening multiple connections with the target server and keeping them open for as long as it takes for the server to crash.
An attack usually consists of sending a partial HTTP request nonstop. These connection requests then fill up the target server’s connection room and cause a denial of any further connection requests, thereby leading to server downtime for legitimate users.
Layer 7 DDoS attacks can compromise your business, and only a few organizations have the resources to reroute and mitigate the attacks. However, there are some ways you can reduce layer 7 DDoS attacks.
One crucial preventative approach is implementing real-time measures like constant monitoring and enabling real-time visibility. By monitoring your traffic constantly, you obtain high-level and in-depth ideas of the typical traffic your application receives. This also helps make identifying an unusual, suspicious, or malicious spike easier. When paired with real-time alerts, real-time visibility enables you to stay aware of — and support your response to — any abnormalities in traffic.
Setting up specific custom rules and policies in your Web Application Firewall (WAF) helps improve the intelligence and filtering ability of the WAF. This can help you detect an ingenuine boost in traffic before it can impact your servers or website. For example, you can add rate-limiting rules on your WAF to block clients from receiving an abnormal number of requests to your application, server, or website.
One method is to employ behavioral analytics that uses artificial intelligence and machine learning to observe user behavior on a website or server. Analyzing user logs and metrics, any slight deviation from the norm can be detected, marked as suspicious, and reported to developers in real-time. Then, you can review the report and conduct more analysis to confirm whether the increase in traffic is malicious.
Employing security experts with proficient knowledge of cyber security best practices also helps mitigate layer 7 DDoS attacks. These experts comprehensively understand the right mix of methods, tools, and infrastructure needed to defend against layer 7 and other forms of DDoS attacks. With this expertise in tow, they can, for example, help write custom policies for your WAF.
