How to Prevent DoS Attacks

What is a DoS Attack?

DoS is an acronym that stands for Denial of Service. It's a type of cyber-attack that targets websites, servers, or networks flooding them with traffic to overwhelm them and make them unavailable to legitimate users.

You may also see the acronym DDoS, which stands for Distributed Denial-of-Service attack. This is just a slightly different type of DoS.

A DDoS involves using multiple computers or devices to coordinate the flood of traffic or requests to the targeted system. This distributed method makes it harder to mitigate, as the traffic comes from multiple sources.

DoS vs DDoS: what's the difference?

Let's use a non-technical analogy of a pizza joint to explain a little further...

Say you run a successful pizza takeaway restaurant, you take orders over the phone and customers pick them up. But one day, a prankster calls and places multiple fake orders, never coming to collect. These fake orders overwhelm your pizza chefs, waste valuable resources, and prevent you from catering to your real customers.

With a DoS attack, you can simply block the prankster's number so they can't make any more calls. In a DDoS attack, however, the calls are distributed. They are coming in from multiple pranksters rendering it almost impossible to determine a prank call from a real call. You could block all the calls, but then you'll inadvertently block real customers in the process. The result? Your pizza service is brought to a grinding halt.

It's a similar situation when it comes to an attack on a server, system, or network.

While Denial of Service attack prevention is relatively simple when it's just a case of blocking one malicious client, preventing a DDoS attack is much more challenging. It requires identifying and blocking multiple sources of fake traffic without blocking legitimate users. For the hackers, DDoS attacks are much more successful. So, these days, most DoS attacks are DDoS!

Now you have an understanding of what a DoS attack is and the challenges of denial of service attack prevention, you might be asking...why?

Why do cybercriminals want to overwhelm a system?

What is the point of a DoS attack?

Well, as we've just mentioned, a DoS attack disrupts the normal functioning of a system, website, or network. The main aim of that disruption is to cause as much inconvenience as possible to the end users and significant financial losses to the targeted organization.

The reasons though can be many!

Here are just a few of the most common reasons for a DoS attack:

Gain competitive advantage: DoS attacks can be a way for an attacker to gain a competitive advantage over another business and poach potential customers. By rendering a website or service unavailable, customers may be driven to the attacker's own website or services instead.

Smokescreen for other malicious activity: DoS attacks can be used to divert attention so that the attackers can carry out other malicious activities. While your security team is busy dealing with the DoS attack, the bad actors could be stealing sensitive data or installing malware.

Political or social activism: DoS attacks can be used as a tool for political or social activism to disrupt the online presence of a government, organization, or individual. The hacktivist group “Anonymous” often uses DoS attacks as part of its arsenal.

Cyber warfare: DoS attacks are often used in cyber warfare to disrupt the enemy's ability to communicate, operate, and defend itself. The attacks may be government authorized or conducted by terrorist organizations, criminal groups, or individuals acting alone.

What are the different types of DoS Attacks?

There are several types of Denial of Service attacks, each with its own unique characteristics and methods of execution. Understanding the different types is an essential part of learning how to prevent DoS attacks.

Here are some of the most common types of DoS attacks.

Flood attacks

Flood attacks involve sending a large amount of traffic or requests to a system, overwhelming its capacity to handle them. Typically, the attacker uses multiple compromised systems or botnets to generate traffic, making it difficult for the target to filter out the attack traffic.

The attack traffic can take various forms, including ICMP (Internet Control Message Protocol) requests, TCP (Transmission Control Protocol) SYN packets, or UDP (User Datagram Protocol) packets. The aim of a DoS flood attack is to exhaust the target system's resources, such as bandwidth, CPU, or memory, making it unable to handle legitimate traffic.

Amplification attacks

Amplification attacks are a type of distributed DoS attack where an attacker uses vulnerable systems to amplify the amount of traffic sent to a target server. In an amplification attack, the attacker first identifies vulnerable systems, such as open DNS resolvers or NTP (Network Time Protocol) servers, that can be used to amplify traffic.

The attacker then spoofs the source IP address of the traffic to make it appear as if it's coming from the target server. The vulnerable systems then respond to the spoofed requests, sending a large amount of traffic to the server. The traffic will ultimately overwhelm the target server's bandwidth and resources, making it inaccessible to legitimate users.

Application-layer attacks

Application-layer attacks target web applications or web services. It attacks the software application running on the server, rather than the server itself.

The aim of an application-layer DoS attack is to overload the application with traffic or requests, causing it to slow down or crash. This can be achieved by exploiting vulnerabilities in the application's code or by using a high volume of requests that mimic legitimate traffic.

One example of an application-layer DoS attack is the HTTP flood attack. The attacker sends a large number of HTTP requests to a server to overwhelm its resources. This can cause the server to become unresponsive, resulting in a denial of service for legitimate users.

Another example is the Slowloris attack, where an attacker sends a large number of incomplete requests to a server, keeping the connections open for a long time. This exhausts the server's resources, making it unable to handle legitimate requests.

How to detect a DoS attack?

Minimizing the impact of a DoS attack means stopping it as soon as possible. But since you don't normally browse your own website, you might not realize something is wrong until your clients or customers start to complain that they can't access your site. By that time, your site may have been under attack for hours, meaning loss of service, income, and revenue.

Of course, the accessibility issues could be a number of things— perhaps it's a server or hosting problem? But figuring these things out takes precious time which will be costing your business in revenue and reputation.

Of course, some DoS attacks will be blatantly obvious.

For example, if you're the victim of a Ransom Denial of Service (RDoS), then you're going to know about it pretty quickly as the attackers will serve you with a ransom demand. Or, if your country is currently at war with another nation, and your website is crashing due to a surge of traffic from IP addresses in the enemy country, then chances are, it's a DoS attack.

But not all DoS attacks are so obvious.

To help speed things along here are some common signs that may indicate a DoS attack is taking place:

• Slow or unresponsive system: Your system or network may become slow or unresponsive, as it is overwhelmed by the flood of traffic or requests.
• Unusual traffic patterns: There may be a sudden increase in traffic or it may be coming from unexpected sources.
• Error messages: Users may be receiving error messages such as "Service Unavailable" or "Connection Timed Out" when attempting to access your site.
• Unusual system behavior: Your system or network may exhibit unusual behavior, such as crashing or rebooting unexpectedly.
• Unusual packet types: DoS attacks often use specific types of packets, such as ICMP or UDP packets, to overload the target system or network. By analyzing the packet types and volumes, you may be able to identify that an attack is taking place.

My website is under a DoS attack...what do I do?

What if it's too late to implement denial-of-service attack prevention measures? If you are currently experiencing a DoS attack on your website follow these steps to mitigate the attack:

Maintenance mode: Put your website into maintenance mode to prevent loss of website data.

Get the word out: Contact your internet service provider (ISP), hosting provider, and any third parties that you may use for service delivery or security management. Let them know that you are under attack and depending on their level of scope, they will be able to help you identify the source of the attack and provide you with solutions or DoS protection.

Block the IP addresses of the attackers: Use network monitoring tools, such as intrusion detection or prevention systems (IDS/IPS) or firewalls, to identify the source IP address of the attack traffic. Then block traffic at the network perimeter by configuring access control lists (ACLs) or firewall rules.

Increase your server's capacity: If your server is being overwhelmed by the DoS attack, you may need to increase its capacity by adding more resources such as CPU, memory, and bandwidth.

Use a CDN: A Content Delivery Network (CDN) can help mitigate the impact of a DoS attack by distributing the traffic across multiple servers. This can help prevent your website from being overwhelmed by a single source of traffic.

Monitor your website closely: Keep a close eye on your website's traffic and performance, and be prepared to take additional action if the attack persists.

How to Prevent DoS Attacks

Here are 10 easy-to-follow tips on how to prevent DoS attacks to ensure the continued availability of your systems and networks:

1. Use a DoS protection service: Consider using a dedicated denial of service attack protection service, which can identify and block incoming DoS attacks before they reach your network.
2. Implement rate limiting: Configure your network devices, servers, and applications to limit the rate of incoming traffic to a level that your infrastructure can handle.
3. Keep your software up to date: Regularly patch and update all software components, including operating systems, web servers, and applications, to fix any known vulnerabilities.
4. Use firewalls: Implement firewalls at your network perimeter to block traffic from unauthorized sources.
5. Monitor your network traffic: Use network monitoring tools to identify and track unusual spikes in traffic, which could indicate a DoS attack in progress.
6. Use intrusion detection and prevention systems: Implement intrusion detection and prevention systems (IDPS) to automatically detect and block suspicious traffic patterns.
7. Educate your employees: Train your employees on how to identify and avoid social engineering phishing attacks, which can be used to launch DoS attacks.
8. Disable unnecessary services: Disable any network services or protocols that are not required for your business operations, as they may provide an easy entry point for attackers.
9. Configure network devices securely: Configure your network devices with secure passwords, and disable any unnecessary management interfaces to prevent attackers from gaining unauthorized access.
10. Develop and test a disaster recovery plan: Create a disaster recovery plan that outlines the steps to take in the event of a DoS attack, and test the plan regularly to ensure its effectiveness.

One of the greatest tips we can give you for Denial of Service attack prevention is to be prepared— the more you know, the better you can protect your business. By understanding what a DoS attack is and how they work you can begin to put in place the preventive measures discussed above to ensure the continued availability of your systems and networks, and safeguard against the damaging effects of DoS attacks.

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