How To Prevent a DDoS Attack

DDoS attacks have increased in frequency, and also have evolved to be more advanced and sophisticated than ever.

A basic volumetric DDoS attack involves overloading an IP address with a large volume of traffic. However, there are other types of DDoS attacks like the flood attack, where the server is flooded with requests, and there are also application-level DDoS attacks which can be much larger in scale. 

However, while preventing a DDoS attack can be a challenge, it is not impossible. In this guide, we will discuss the details of a DDoS attack and  several ways you can prevent a DDoS attack,

How DDoS Attack Works

To successfully prevent a DDoS attack, we first need to understand how our website works and how a DDoS attack will disrupt this process. In its basic principle, here is how your website operates: 

1. Visitor access your website’s URL, and so this user’s web browser sends a packet or request to your website’s server
2. Your web server receives this packet and then fetches the necessary data according to the user’s request, and sends it back to the user’s web browser.
3. The user’s web browser receives this data, and then use this data to display the content of your website

Although DDoS attacks come in various different forms, they all work based on this process discussed above. Your web server has only a limited amount of resources and each request from a website visitor uses a certain amount of server resources. Since your server resources are limited, there’s a limit to how many browser requests can be processed at a time. 

When your server processes too many requests, your website can crash, causing downtime. A DDoS attack exploits this ‘weakness’ by flooding your server with more requests than it can handle. 

Now that we’ve understood the basic principle of how a DDoS attack works, we can properly discuss how we can prevent these DDoS attacks from affecting our website.

Develop a DDoS Response Plan

An important thing to note about a DDoS attack is that by the time you’ve detected an incoming attack, it might be too late to plan a response. Time is of the essence in any DDoS attack, and responding just a few minutes earlier can either make or break your success rate in preventing the attack and/or mitigating the damage. 

This is why preparing a response plan ahead is very important so you can ensure prompt reactions. You should develop a comprehensive DDoS prevention plan based on a thorough assessment of your network and/or system. The bigger your system and the more complex your infrastructure is, the more complex your DDoS response plan should be. 

The objective of a response plan s to ensure your team and key members are aware of their responsibilities during the attack, and to ensure the required system/solutions are properly prepared. This way, we can mitigate the impact of a DDoS attack and preferably preventing it from happening altogether. 

Here are the key elements of a proper DDoS response plan:

• System audit: it’s important to list all assets that might be affected by any DDoS attack (even if it’s only a potentially small impact). This step also includes the required equipment like filtering tools (including third-party cloud-based services), threat detection measures, and security-enhanced hardware is in place.
• Response team: define key responsibilities for those who are going to be accountable in the time of a DDoS attack. This is to ensure an organized, speedy reaction to the incoming DDoS attack as it happens. `
• Escalation procedures: design a notification protocol so your team members know exactly who they should contact (if any) in case of a DDoS attack.
• Communication protocols: include the list of external and internal contacts that should be informed in time of the attack. This includes cloud-service DDoS mitigation provider(s), ISP, any security vendors, and even your customers.

Practice Basic Network Security

The most basic—but very important—DDoS prevention approach is to ensure you have as little human error as possible. 

Implement strong security practice in your whole team, including but not limited to:

• Strong password

Make sure all passwords are unique (never been used anywhere else), and at least 12 characters long while including the combination of alphabets (both upper and lowercase), numbers, symbols, and alphabets. There are various random password generator tools that can help you in this aspect. Also, change your password on a regular basis.

• Education

Educate and train your team with the up-to-date knowledge on various cybersecurity threats (that can allow vulnerabilities for DDoS), and repeat this training regularly. 

• Reduce attack surface exposure

The idea here is to reduce the ‘surface area’ that is potentially vulnerable so you can minimize the options for the attackers to orchestrate DDoS attacks. This can be done by: 

1. Using a Content Distribution Network (CDN) service combined with Web Application Firewall (WAF) to limit the possibility of attackers reaching your original server. All content is spread to the CDNs across the globe and all requests are serviced only from them. On the other hand, requests for uncached content must 
2. Implementing load balancers to protect servers and essential resources from exposures to DDoS by placing these assets ‘behind’ the load balancers
3. Removing any irrelevant services, unnecessary features, and ensuring all applications are up-to-date. This is to eliminate vulnerabilities that are often leveraged in DDoS attacks as points of entry.

• Firewalls

While firewalls can’t protect you from complex DDoS attacks, they can help the DDoS prevention system by protecting your network from various security issues. 

By ensuring your website and/or application is clean from security loopholes and weaknesses, you can eliminate the potential point of entry of the DDoS attack. You have to ensure your network is properly secured with holistic security measures. 

Monitoring Your Website Traffic

An integral aspect of preventing a DDoS attack is to constantly monitor your website traffic for the suspicious and sudden increase of traffic–which is a telltale sign of a volumetric DDoS attack.

Volumetric DDoS attack is the most common type of DDoS attack which mainly affects the network and/or transport layer of the OSI model (layer-3 and layer-4 attacks). So, a dramatic increase in traffic is a very important sign of this DDoS attack. Make sure to set up the right monitoring tools in place, and regularly check your traffic logs from time to time. 

However, a surge in traffic is not the only sign of a DDoS attack. More sophisticated DDoS attacks can be low-and-slow. There are cases where the DDoS attack only attempts 1 request per second but targeting a very vulnerable endpoint. So, there are other indications to monitor from your traffic, namely: 

• The location source of the incoming traffic. If you suddenly getting traffic from Kazakhstan while you are a local website based in Maryland, it can be a red flag.
• The time of day of the request. If there’s a routine visit within a very similar timeframe each day (creating a pattern/schedule), you should take notes of this.
• The time of year these visits occur. For example, surges during holiday seasons might be common, but remember that the attackers can mask their traffic during the expected spikes. 

More advanced DDoS prevention solutions like DataDome can differentiate between malicious traffic and legitimate traffic, and so it will only block the bad bot traffic and allow real traffic. They typically combine an anomaly detection and application-level controls while monitoring some factors like:

1. Noticing excessive requests from a certain source. DDoS attack bots typically request more often and much faster than real human users. Typically when it’s difficult to differentiate between malicious and legitimate traffic, challenge-based tests (i.e. CAPTCHA) are conducted to provide a more accurate assessment of the traffic and the motives.
2. Discerning between malicious and legitimate requests by analyzing attributes like HTTP protocols. Malicious requests typically do not conform to standard attributes like redundant HTTP headers, requesting pages that don’t exist, purposefully delivering slow response time, and so on. 
3. Watching and predicting known and unknown attack signatures like detecting the possibility of IP spoofing, TCP handshakes, fragmented packets, and so on. 

Prepare Multi-Layered DDoS Defense

Since, as mentioned, modern DDoS attacks can target different layers of the OSI model or combine them together, it is now necessary to implement a multi-layered DDoS protection system in place.  

Ideally, the DDoS prevention system should be able to both identify and mitigate/absorb incoming DDoS attacks. And, the DDoS prevention solution shouldn’t only protect against layer-3 or 4 volumetric attacks, but all types of attacks including the most sophisticated layer-7 (application level) DDoS attacks and various other OWASP automated threats. 

At the same time, the DDoS prevention solution should be able to scale massively to accommodate today’s massive DDoS traffic. The average DDoS attack nowadays is getting larger and much more amplified, and so the prevention system must be able to handle this. 

Make Use of Cloud-Based Solutions

Nowadays, we have the option of outsourcing our DDoS prevention to cloud-based providers, which offer several important advantages related to DDoS mitigation.

First, we can have a much larger bandwidth on the cloud when compared to an on-premise, hardware-based system of the same price. Huge bandwidth is very important in defending ourselves from today’s massive-scale volumetric DDoS attacks.

Second, the nature of cloud computing itself allows us to ‘mask’ our original server and so these cloud-based apps and servers can first absorb the malicious traffic before it reaches our main server. Last but not least, these cloud-based services are managed and monitored by professional engineers whose job consists of understanding the latest DDoS tactics. So, you can reduce your human resource costs while ensuring a 24/7, always-on protection.

End Words

Preparation and a proper response plan are the most important things for your organization in preventing a DDoS attack. On the other hand, preventing a DDoS attack is far better than stopping it, because when a DDoS attack is underway and succeeds in crashing down your website, getting it back to normal can be extremely expensive and can take a lot of time.

The threats of DDoS attacks are very real and are no longer a threat exclusively for massive enterprises and big corporations. In fact, cybercriminals are increasingly targeting small and medium-sized companies because they think these smaller companies are more vulnerable (which in most cases, is a fact). So, a multi-layered DDoS prevention system is no longer a luxury, but a necessity for all businesses of any size.