HTTP Flood Attack

Cyber crimes are increasing with the growing demand for the internet. With an increasing number of cybercrime cases reported each year, awareness of cyberattacks is very important. Cyber crimes/cyberattacks are done by hackers who unethically want to breach user data and steal sensitive information from the user accounts. The purpose behind cyberattacks is mostly related to personal or organizational gains, which may be achieved financially or emotionally.

In the HTTP Flood Attack the attacker attacks the target server with a massive number of authenticated HTTP requests, to the websites until the website or web application becomes inaccessible to others, it is also a type of DDoS (Distributed Denial-of-Service) attack. Unlike the volumetric DDoS attacks, HTTP Flood Attacks both are operate at Layer 7 (Application Layer), which making them difficult to distinguish that it is normal traffic or malicious traffic.

In this article, we will cover everything you need to know about HTTP Flood Attacks which includes how they work, what are the impact, different attack methods, detection techniques, and best practices for prevention and mitigation of this attack.

What is an HTTP Flood Attacks?

An HTTP Flood Attack is a malicious attempt to exhaust a server’s resources by sending an overwhelming number of HTTP GET or POST requests. Unlike traditional DDoS attacks, these attacks don’t rely on high-bandwidth but instead manipulate legitimate HTTP requests to cripple web applications. Most of the attackers often use botnets or compromised devices to generate the flood of requests.

• HTTP flooding attack is a layer 7 (Application Layer Attack) which is really dangerous and harmful as it is easy to attack websites using HTTP flooding. 
• HTTP flooding is a form of DDoS (Distributed Denial of Service) where an HTTP flood attack makes use of HTTP to get an HTTP post requests to carry out the cyberattack.
• The huge number of HTTP requests make the site/ server unresponsive and thus bring them down and inaccessible for use.

Types of HTTP Flood Attacks

HTTP flood attacks target the vulnerabilities in the application layer (Layer 7) of the OSI model and their are various ways to target a web servers. In this attack malicious request as disguise themselves as legitimate requests which making them hard to detect and the server thinks that it is normal traffic. Below are the most common types of HTTP flood attacks, their mechanisms, and real-world attack scenarios.

1. HTTP GET Attack

• This method enables attackers to send numerous requests using HTTP GET towards the target server.
• Since these requests look legitimate on the surface, distinguishing them from authentic user traffic is quite complex.
• The server tries to address every single request by initiating multiple processing sessions which ends up consuming server resources.

Example:

• Attackers repetitively send requests to download various large files such as images, videos and pdfs.
• This single action can entirely disable the website in case the server gets overloaded as well as significantly raise the bandwidth utilization.

Impact:

• This ends up causing high CPU alongside memory usage.
• The websites get noticeably weaker or even entirely stop server response.

2. HTTP POST Attack

• Unlike GET flood attack, POST flood attack involves much more complex requests, meaning that it is more difficult to execute than GET floods.
• These requests also need a server to process their content thus the impact of the attack is greater.
• Typically these forms of attack are made against form fillers, API terminals, or even login sections.

Example:

• A hacker submits login forms repeatedly, forcing the server to validate credentials each time.
• Repeatedly submitting the login form consumes processing power of the server which affects the authentication system of the website and disrupting the real users also to perform their tasks.

Impact:

• The process involves large amounts of CPU power since the database receives numerous queries in each single attempt.
• Results on login portals, web applications which require active user validation alongside shopping carts can suffer immensely.

3. Slowloris Attack

• Slowloris opens the multiple HTTP connections but never completes the request.
• So that server keeps open the connection because the server is waiting for the full request arrival.
• Which prevents the new legitimate connections from being processed or to process new legitimate requests..

Example:

• The attacker slowly but surely sends partial HTTP headers towards completion.
• The server, waits indefinitely to receive the rest of the headers, gets congested in waiting.

Impact:

• Very harmful for web servers using Apache.
• Has the capability to take down websites with a relatively low volume of requests in comparison to other attacks that make use of flooding.

4. Recursive HTTP Flood Attack

• In this the attackers send requests through different URLs recursively which increasing the workload exponentially.
• Which make the server slow and gradually, the entire website accessible URL structure will be crawled causing a strain on the databases and backend processes.

Example:

• Attacker goes from /home → /products → /contact repeats while adding different parameters until the website structure is completely changed.
• Each request is forces the server to render a new page dynamically by bypassing the caching.

Impact:

• It can bypass the caching mechanisms which forcing the real-time server-side processing for every request.
• Has a negative impact on the web applications to the extent that it increases the database query for the application causing it to slow down.

5. Randomized URL HTTP Flood

Attack Method:

• Attackers have the ability to continuously change URL parameters so that they are able to create unique request URLs and as a result caching becomes impossible.
• Each request is treated like a new page fetch, leading to an increase in server processing time.

Example:

• /index.php?sessionid=12345 → /index.php?sessionid=67890 → /index.php?sessionid=54321
• Each modification forces the server to address requests separately instead of retrieving saved answers.

Impact:

• Bypasses CDN and caching protections.
• Makes rapid use of server resources which leads to server downtime.

HTTP Flood Attack vs. Other DDoS Attacks

Different classifications of DDoS attacks exist, each with a unique goal for specific portions of the network. One of the more advanced types of DDoS attacks is the HTTP Flood Attacks which seek to sabotage web servers by pretending to make real HTTP requests. These are volumetric DDoS attacks, but in contrast to other volumetric attacks, they do not depend on raw bandwidth consumption. As the attacks use application vulnerabilities instead, they are more difficult to deal with.

To understand the similarities and differences between common DDoS attacks and HTTP Flood Attacks, , let’s break them down in the table below.

How Can an HTTP Flood Be Mitigated?

An HTTP Flood attack is a form of DDoS attack in which numerous spurious HTTP requests inundate a web server, draining resources and rendering the website inaccessible. The attack is usually practiced in cybersecurity testing labs with Kali Linux online, Kali Linux browser, or Kali Linux cloud platforms for ethical hacking and penetration testing.

To prevent an HTTP Flood attack, use the following measures:

• Rate Limiting – Limit the number of requests per IP in a Linux terminal online with commands such as:

iptables -A INPUT -p tcp --dport 80 -m limit --limit 20/min -j ACCEPT    # This helps prevent excessive requests from a single source.

• Web Application Firewall (WAF) – Utilize cloud-based DDoS protection tools such as Cloudflare, AWS Shield, or Akamai to block malicious requests.
• Traffic Monitoring – On an online cloud instance of Kali Linux, utilize tcpdump, htop, or netstat to inspect abnormal traffic spikes.
• Challenge-Response Mechanisms – Add CAPTCHAs and JavaScript-based verification to distinguish bots from users.
• Load Balancing – Balance traffic between more than one server to avoid a single point of failure.
• Geo-Blocking and Blacklisting – In case HTTP Flood attacks are coming from a certain region, block those IPs using firewall rules.

Also Read:

• DDoS Attacks in Blockchain
• Denial of Service and Prevention
• What is Distributed Reflection Denial of Service?

Conclusion

HTTP Flood Attacks pose a serious threat to web applications, businesses, and critical online services. Their ability to mimic real traffic makes them challenging to detect and mitigate. However, by implementing rate limiting, web application firewalls, CDNs, and behavioral analysis tools, organizations can effectively protect themselves against these attacks.