Applications nowadays have become a primary tool to run organizations, reach out customers, and engage with them. This has accelerated the shift to digital first, and with it, become an integral component of an organization’s digital stack. However, they have also exposed organizations to new security threats owing to the expanded attack surface.
Application layer DDoS attacks is one such problem organizations face because of their overreliance on applications. Hackers use this to extract data, shutdown networks and damage companies with ransom quests.
Various reports also confirm the growing threat. An Infosecurity Magazine report in 2023 says that such attacks account for almost 56% of all DDoS attacks on AWS.
In this blog, we will discuss in detail about application layer DDoS attacks, its types, how application layer attacks work, and effective strategies to mitigate such attacks.
What is Application Layer DDoS Attacks?
Application layer DDoS attack, or Layer 7 DDoS attacks, are dangerous and sophisticated methodologies that target user-facing apps and networks. They are typically application layer attacks targeting protocols that run over HTTP or DNS with the goal of disrupting services.
In these attacks, threat actors bypass the network with minimal bandwidth, and that is why it can be difficult to trace and prevent these attacks through traditional defense mechanisms.
Hackers generally use request floods, application vulnerability exploitation (including Apache Range Header and URL, service information disclosure via null byte output), application-specific attacks, such as XML-RPC floods, or zero-day vulnerabilities may be employed.
Difference Between Network Level DDoS Attack And Application-Level DDoS Attack
Distributed Denial of Service (DDoS) attacks can be extremely dangerous. This can disrupt the normal functioning of a targeted server, service, or network by overwhelming it with huge Internet traffic.
Such attacks can be categorized into two primary types: network-level and application level attacks. Understanding the differences between these two types is crucial for implementing effective defense strategies. Below is a comparative overview that highlights their key characteristics and distinctions.
| Feature | Network-Level DDoS Attack | Application-Level DDoS Attack |
| Target Layer | Network Layer (Layer 3 and 4) | Application Layer (Layer 7) |
| Goal | OverwhelmS bandwidth and network resources | Consume application resources and server capacity |
| Common Techniques | SYN Floods, UDP Floods, DNS Amplification | HTTP Floods, Slowloris, Buffer Overflow |
| Detection Difficulty | Easier to detect and mitigate | More difficult to detect and mitigate |
| Traffic Type | High volume of traffic, often illegitimate | Seemingly legitimate requests from multiple sources |
| Mitigation Strategies | Rate limiting, packet filtering, next-gen firewalls | Web Application Firewalls (WAF), CAPTCHA tests |
| Resource Consumption | Primarily consumes network bandwidth | Consumes server and application resources |
| Impact on Services | Can disrupt overall network availability | Can slow down or completely shut down specific services |
| Example Attacks | DNS amplification, NTP reflection | HTTP floods, targeted API requests |
Types of Application-Layer DDoS Attacks
Instances of Distributed Denial of Service Attacks have become commonplace. Here are some notable examples of application layer attacks:
1. HTTP Flood Attacks
In such attacks, threat actors send a large number of HTTP requests to a web server within a short span. This consumes resources and denies legitimate requests. Such attacks are difficult to distinguish from legitimate traffic.
2. Slowloris
Such attacks involve sending partial HTTP requests to a server. This keeps connections open for as long as possible, and as a result, the server becomes overwhelmed. This eventually leads to denial of requests for many legitimate requests.
3. Slow Read Attacks
In this scenario, attack vectors deliberately read data from the server very slowly. This ties up server resources and prevents it from serving legitimate requests.
4. XML-RPC Floods
In this attack, hackers exploits the XML-RPC protocol( (Extensible Markup Language Remote Procedure Call). They do it by sending numerous requests that can overwhelm the server, especially when it’s not properly configured to handle such traffic.
5. Application-Specific Attacks
These attacks target specific vulnerabilities within an application, such as exploiting poorly designed APIs to send excessive requests or manipulate the server’s behavior.
7. Ransom DDoS (RDoS)
Attack vectors threaten to launch an application layer attack unless a ransom is paid. This can involve overwhelming the application with requests until the victim complies.
8. Brute Force And Credential Stuffing Attack
Brute force and credential stuffing attacks are some other kinds of attack that are not fully similar to DDoS attack, but their automated nature looks closer to DDoS attacks.
How Application Layer DDoS Attacks Work
During the attack, attack vectors target the topmost layer of the OSI model. This is the layer at which the end users of the application operate. They identify vulnerabilities in this layer and attack it to exploit these security loopholes.
They use a simple mechanism for the purpose. Advanced application layer attacks, particularly HTTP GET and POST requests flood are common methods used to overwhelm web servers and applications. These attacks exploit the HTTP protocol to disrupt services and deny access to legitimate HTTP requests.
In an HTTP GET flood attack, threat actors send a massive number of HTTP GET requests to a targeted server. The purpose of this activity is to exhaust the server’s resources. HTTP POST floods send massive amounts of data to the server.
They do it by using a simple concept: the resources required to process a request (like database queries and server-side logic) are considerably higher than what is needed to send the request itself. As a result, the resources get consumed very quickly.
One challenge with HTTP flood attacks is detection, as the requests are valid HTTP and can blend in with normal traffic. Traditional security measures may not be effective in dealing with such attacks.
Another common technique in application layer attacks is the “low and slow” method. In such attacks, attackers send requests at a slow rate to avoid detection. Such tactics can lead to a denial of service without generating a large volume of traffic that would trigger traditional DDoS defenses.
Most of the application layer attacks are carried out by gaining unauthorized access to Internet of Things (IoT) devices or botnets. They can mimic legitimate user behavior, making it difficult for security systems to distinguish between attack traffic and genuine requests.
Why Application Layer DDoS Attacks Are Hard to Mitigate
Application layer DDoS attacks are complex. They exploit specific protocol and application vulnerabilities, which makes these attacks devastating and difficult to mitigate. These attacks target the complexities of protocols like HTTP, SMTP, and FTP, using techniques such as HTTP GET/POST floods and Slowloris attacks. Hence, it is not easy to block application layer attacks.
What makes application-layer attacks challenging is that attackers can cripple the application with just a few hundred requests per second, consuming considerable server resources.
Additionally, detection and mitigation of these attacks pose significant challenges:
- Traffic normalization: This makes it difficult for volume-based detection systems to identify threats, as attack traffic often mimics legitimate requests.
- Anomaly detection: Many systems face limitations as attackers can modify their tactics in real-time to avoid detection.
- Complexity of application layer protocol: The intricacy of application layer protocols requires deep packet inspection capabilities that many traditional security solutions lack.
- Adaptive techniques: Attackers employ adaptive techniques, varying request patterns and utilizing botnets to evade defenses. This adaptability makes it challenging to block malicious traffic without affecting legitimate users.
- Insufficient protection: Many organizations are inadequately prepared to defend against these attacks. For example, insufficient Web Application Firewall (WAF) configuration leaves systems vulnerable to specific attack patterns.
Furthermore, lack of proper rate limiting allows servers to be overwhelmed by rapid requests from a single source.
Application Layer DDoS Attacks: Real World Case Studies
These incidents illustrate the growing sophistication and prevalence of application layer DDoS attacks, emphasizing the need for robust security measures to protect against such threats. Here are three real-world incidents of application layer DDoS attacks:
1. AWS Application Layer Attacks
In 2023, it was reported that 56% of DDoS attacks targeting Amazon Web Services (AWS) customers were application-layer attacks. These attacks often involved a common method. Attackers mimicked legitimate traffic, making them difficult to detect.
The increase in application-layer attacks was attributed to the growing trend of attackers using DDoS-for-hire services. The attacks targeted various applications hosted on AWS, leading to significant disruptions for affected businesses.
2. Retail Sector Attacks During Black Friday
During the Black Friday sales period in the US in 2023, a notable surge in application layer DDoS attacks was observed, particularly targeting retail and e-commerce websites. Cloudflare reported a 117% year-over-year increase in network-layer DDoS attacks, but application-layer attacks also saw a significant uptick.
Attackers aimed to overwhelm retail websites with HTTP request floods, leading to service outages and impacting online sales during a critical shopping period.
3. Taiwan’s Increased DDoS Activity
In 2023, Taiwan experienced a staggering 3,370% increase in DDoS attack traffic, with a significant portion being application-layer attacks. These attacks targeted various sectors, including government and financial institutions, aiming to disrupt services and create chaos.
The attackers utilized techniques that overloaded the application servers with seemingly legitimate requests, effectively denying service to real users. This incident highlighted the vulnerabilities of critical infrastructure to sophisticated application-layer DDoS attacks, prompting a reevaluation of security measures across the region.
Effective Mitigation Strategies for Application Layer DDoS Attacks
DDoS attacks on application layers are serious threats for web app availability and performance. Hence, organizations need to adopt effective mitigation strategies. They need to be proactive to prevent such attacks.
Here are some proven techniques for defending against these sophisticated threats by organizations:
1. Web Application Firewalls (WAFs)
WAFs act as a protective layer between web applications and incoming traffic, working as a critical line of defense for application-layer DDoS attacks. They analyze HTTP requests and responses and filter out malicious traffic from legitimate requests. A well-configured WAF can protect against common application layer attacks like HTTP floods and Slowloris attacks.
Organizations can block malicious traffic by implementing rules specific to application. If the requests have anomalous patterns, WAF can block such traffic.
WAFs can also block or redirect such traffic coming from specific geographic regions or within a defined region that doesn’t fit the application’s normal traffic patterns.
Hence, regular updates and tuning of WAF policies are essential to stay in tune and keep pace with evolving attack techniques.
2. Behavioral Analytics and Machine Learning
Behavioral analytics involves monitoring traffic patterns to establish a baseline of normal behavior. Once this has been done, machine learning algorithms may identify deviations from this baseline which will indicate possible DDoS activity occurring somewhere within the system.
3. Rate Limiting and Throttling
Implementing rate limiting helps control the number of requests a user can make within a specified timeframe. Setting thresholds for incoming requests allows organizations to prevent any single user or IP address from overwhelming the server.
Throttling can also be applied to slow down excessive requests, ensuring that the server remains responsive to legitimate users. This technique is particularly effective against HTTP flood attacks, where attackers attempt to exhaust server resources with high volumes of requests.
4. CAPTCHA and JavaScript Challenges
The objective of CAPTCHAs is to help to make a distinction between a human user and an automated bot. In each of the different CAPTCHA challenges, a set of tasks is deployed for the user, and this can only be easily accomplished if the user is human, else it would be very hard to achieve that goal if he is a bot—for instance, recognizing distorted text or selecting images.
CAPTCHAs can prevent bots from performing bot actions like triggering large file download requests or form submission actions by requiring human verification.
5. IP Reputation Filtering and Rate Limiting
The combination of IP reputation filtering with rate limiting provides another layer for application layer DDoS attacks. IP reputation filters run according to a database of known malicious IP addresses. These are the ‘bad actors’ which have been seen earlier with the attack traffic pattern, so it would be difficult to easily attack with the same infrastructure.
Its effectiveness can be increased when implementing this with rate limiting. Still, even behind such an IP address, the requested number can be limited. When integrated with IP reputation filtering, this system lessens the impact of the attacks. During this case, genuine traffic is enabled to get through and reach the application without any hindrance.
6. Cloud-based Mitigation Solutions
Routing traffic through this cloud-based mitigation platform eases the processing burden on an organization’s servers and brings other advanced security features designed for DDoS protection.
In addition, machine-learning-based algorithms with behavioral analysis often detect and mitigate the attack in real time. Using cloud-based DDoS protection services can dynamically absorb large volumes of malicious traffic and cope with sudden increases in traffic.
In addition, cloud services are globally available, providing protection to your application against attackers all over the world.
How SecureLayer7 Can Help
SecureLayer7’s offensive security testing services can help prevent application layer DDoS attacks by identifying vulnerabilities and weaknesses in web applications. Their team of certified security professionals conducts thorough penetration testing to detect and remediate security loopholes.
Key offensive security measures employed by SecureLayer7 ato prevent Application-Layer DDoS attack include:
- Vulnerability Assessments: Identifying security weaknesses in systems and networks, enabling organizations to address critical vulnerabilities before they can be exploited.
- Application Penetration Testing: Ethical hackers simulate real-world attack scenarios to uncover misconfigurations, outdated software, weak access controls, and other vulnerabilities.
- Red Teaming: Going beyond traditional testing to uncover hidden vulnerabilities and weaknesses that may not be apparent through standard assessments.
- Threat Hunting: Proactively searching for indicators of compromise (IoCs) or anomalous behaviors within the network to detect advanced threats.
SecureLayer7’s services help identify and remediate vulnerabilities, reducing the risk of successful attacks and ensuring the availability and performance of web applications.
Conclusion
Application layer (Layer 7) DDoS attacks are highly sophisticated threats targeting websites and applications. Effective defense against application layer DDoS attacks requires a comprehensive security approach, including advanced traffic analysis, properly configured Web Application Firewalls, and robust monitoring systems. Organizations must stay vigilant, continuously updating their security measures to combat the evolving threat landscape.
Don’t let sophisticated application layer DDoS attacks compromise your online presence. SecureLayer7’s cutting-edge solutions can effectively detect and mitigate these complex threats, ensuring your applications remain secure and available. Contact us now to know more about how we can help.
