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What is a DDoS Attack? How Do I Stop One?

One thing’s for sure: a successful Distributed Denial-of-Service attack is devastating. It can result in your organization or website disappearing from the internet, leaving you with no way to interact with your customers.

Therefore, knowing what a DDoS attack is and the best ways to stop one is vital. So, if tomorrow your site is attacked, what will you do? Fortunately, if you lack ideas, then you’re in the right place to get answers.

DDoS mitigation is now an integral part of the technology stack given the ever-rising DDoS attacks that are now more advanced, forceful and prevalent in the modern digital world. However, to be able to stop a DDoS attack, you must be crystal clear about how a Distributed Denial-of-Service attack works, the type of attack that’s occurring, how to monitor for these attacks and ways of preventing them.

Let’s get started.

DDoS lock red on a server room

What Is a DDoS Attack?

It’s very difficult to stop something that you don’t fully understand. The primary purpose of a Distributed Denial-of-Service attack is to overwhelm your website server to either take it down or cripple it.

It forces your server to deny all requests to access your site or service. What makes a DDoS attack even more frustrating is the fact that the attacker gains nothing and typically there’s nothing that’s hacked.

So, what is a DDoS attack? At its core, a DDoS attack is simply a form of a cyber-attack targeting effective systems to disrupt the network service or the connectivity, causing a denial of service for all users of a targeted resource. Usually, the attack can knock your website or service offline temporarily, which can last for several days or longer.

Two people using computers to deliver a DDoS attack

So, how do Distributed Denial-of-Service attacks work? Basically, a user attacks the targeted website with a huge number of service requests, overloading the server.

That way, the services or requests are halted or slowed, meaning the website and its services are unusable. DDoS attacks usually last around 24 hours but, depending on the extent of the attack, they can last even longer.

The attacks are often carried out using many different computers to generate a large volume of requests. These computers often don’t belong to the attackers but have instead been hacked by them to carry out the requests.

While these computers can be regular computers, they can also be IoT devices. IoT devices are often much less secure than regular computers which leaves them vulnerable to hackers who want to use them for their own purposes.

These attacks are referred to as denial-of-service attacks because the server or website can’t serve the required traffic when the attack happens.

They’re also referred to as Distributed Denial-of-Service attacks because the traffic source is distributed across many different computers. However, when the illegitimate traffic is from a single source it’s called a DoS attack.

What makes DDoS attacks harder to block is that the traffic sources are usually distributed across the globe. Now, to help you protect your web apps and site against DDoS attacks you must first understand the common types of DDoS attacks.

Types of DDoS Attacks and How They Work

There’s a plethora of DDoS attacks that all target your systems and network differently. Here are the most common types of DDoS attacks.

Volumetric Attacks

Volumetric attacks are the most common type of DDoS attacks, whereby the machine’s bandwidth is overwhelmed as it’s flooded with false data requests for every available open port on the server. Since the bot overwhelms the ports with false data, the machine must continually check malicious data requests. Therefore, there’s no room for accepting legitimate traffic.

ICMP floods and UDP floods are the two main types of volumetric attacks.


User Datagram Protocol (UDP) is a protocol relating to the transmission of data without checks. On the other hand, the Internet Control Message Protocol (ICMP) is used between the network devices when communicating.

Another type of volumetric attack is an HTTP flood. This is where the server is overloaded with more HTTP requests per second than it can handle. Hence the name “HTTP flood.”

A similar type of DDoS attack is called a DNS flood. This is where the attackers flood the DNS server of a website to overwhelm it. While the target in this case is the DNS server, the outcome is still the same. The DNS server is overloaded and legitimate users are unable to access the site or service.

Application Layer Attacks

A hacker using a laptop

These are the simplest form of DDoS attacks and they mimic routine server requests. The application layer is the outermost layer in the OSI network model.

Moreover, it’s the one closest to a user’s interaction with the system. Attacks using the application layer usually focus mainly on direct web traffic with the potential avenues being HTTPS, SMTP, DNS and HTTP.

It’s often difficult to spot and troubleshoot application layer attacks because these attacks mimic legitimate web traffic. Moreover, application layer attacks use just a few machines, in some cases they use just one, meaning the server can treat the attack as higher legitimate traffic.

Protocol Attacks

Protocol DDoS attacks exploit how servers process data to overload and overwhelm the intended target. In simpler terms, they’re targeted at the parts of the network used for verifying connections. They work by sending purposefully slow or even malformed pings to ensure that the system uses a lot of memory to verify the pings. The server will then wait for confirmation from the source’s IP address, which it never receives.

This malicious traffic reduces the number of pings a server can handle per second. The result is that requests from legitimate sources go unnoticed because the server is too busy dealing with the slow, fraudulent requests.

Also, protocol attacks can target firewalls, whereby they send large amounts of irregular data. Therefore, a firewall alone won’t stop DDoS attacks.

Why Do DDoS Attacks Happen?

You might be wondering: who launches a DDoS attack? The truth is, anyone can carry out a DDoS attack. For instance, a regular person can pay for the attack or even rent a current botnet to carry out their planned attacks.

In fact, some could carry out a DDoS attack just for bragging rights to show off what they’re capable of. However, most folks use DDoS attacks for other reasons, such as:

  • Competitive gamers taking down opponents
  • Business owners trying to beat the competition
  • Trolls enacting revenge on targets
  • Activists that look to prevent individuals from accessing particular content

Who Is Most Vulnerable To DDoS Attacks?

A laptop within a server room delivering a DDoS attack

Usually, when a DDoS attack happens it results in downtime that could hugely impact giant corporations. Therefore, these massive corporations are the primary targets as they could lose billions of dollars. While the attackers don’t gain any money from conducting these attacks, there’s still some payoff in their minds for taking these corporations offline.

However, that doesn’t mean that the average person is excluded from DDoS attacks. While large corporations are often the target, individuals can be targeted as well, potentially for one of the reasons mentioned in the previous section. If you’re the victim of a DDoS attack, keep in mind that you have all rights reserved when it comes to getting your services back online.

How To Monitor for DDoS Attacks

The most challenging thing when it comes to DDoS attacks is the fact that they occur with no warning.

Unlike hackers that sometimes send alerts, DDoS attacks begin affecting your site with no warning at all.

In general, website owners don’t spend their time looking through their own site. This means that only the complaints from customers will notify them that something’s wrong.

A DDoS attack likely won’t be the first thing to come to mind at that point. Instead, you’ll be thinking about your host or server being down. So you check the server and do some necessary tests and you’ll see high network traffic with maxed out resources.

You might proceed to see if programs are running in the background, but unfortunately, you won’t see any. By the time you realize that it’s actually a DDoS attack, it means plenty of hours of missed income that will eventually impact your revenue.

Perhaps the best way of mitigating a DDoS attack is to be aware when it starts to happen immediately. To help you recognize that a DDoS attack is happening, look for the following clues:

Signs of DDoS Attacks

A man using a laptop to put on a DDoS attack

The most common sign is a lot of requests from the same IP addresses. When you realize that there are several connection requests from a range of IP addresses over a short period, then it could be that you’re under attack.

Therefore, you may want to set up your router to send the traffic to NULL routes from some IPs. That way, the attacking IP address can be sent to a dead end and not affect the servers. However, you can sometimes inadvertently block a legitimate IP address using this method.

Other common signs of DDoS attacks include the following:

  • Your server responds with a 503 error as a result of service outages
  • The TTL on the ping requests times out
  • The log analysis solutions indicate a massive spike in traffic
  • When using a parallel connection for internal software and the employees notice a slowness issue


DDoS attacks are definitely a significant security concern. However, you can set some automation and alerts to trigger proactive notifications to help you limit the time taken to identify and stop these attacks.

How To Stop a DDoS Attack

Sometimes the only difference between an organization going offline and thriving lies in knowing how to stop DDoS attacks early. Therefore, before your operations are affected, here are some tips to help you prevent DDoS attacks:

Identify Attacks Early

If you run your own servers, you need to have tips for identifying the exact moment the attack starts. The reason is straightforward: the sooner you establish that it’s a DDoS attack, the sooner you’re able you stop it.

Therefore, the only sure way to have that early knowledge about a DDoS attack is by ensuring that you familiarize yourself with your typical traffic profile.

For instance, once you’re familiar with how your regular traffic looks, it’ll be effortless to spot when the profile changes and specific spikes occur.

Usually, attacks will start with sharp spikes in your traffic. At that moment, once you’re aware of your regular traffic, you can tell the difference between the start of a DDoS attack and a sudden surge in legitimate visitors. Also, as much as you familiarize yourself with your traffic, you don’t need to take anything for chance, but ensure that you nominate a DDoS leader that can be responsible for taking action in case you come under attack.

Take Immediate Action

If you’re running your own web server, then you need to defend at the network perimeter. Some technical measures can help to partially mitigate a DDoS attack, especially during the initial minutes of the attack.

Most of these measures are simple. They are as follows:

  • Drop malformed or spoofed packages
  • Rate limit the router to prevent the web server from getting overwhelmed
  • Set slower ICMP, UDP and SYN flood drop thresholds
  • Add filters to instruct the router to drop packets from the apparent attack sources
  • Timeout half-open connections aggressively


All these measures have worked well in the past, but given that DDoS attacks are a bit larger nowadays, these measures are unable to stop a DDoS attack completely. However, they’ll buy more time to get to the core of the DDoS attack to stop it.

Overprovision Bandwidth

A man using a touch screen on a DDoS attack

If you thought you didn’t need more bandwidth for the web server, you might want to think again. Generally, it makes a lot of sense to have more bandwidth than you might need. It’s a perfect way to accommodate sudden, unexpected traffic surges that may result from a special offer, an advertising campaign or a mere mention of your organization in the media.

Also, while overprovision may not be the complete solution to stop a DDoS attack, it will buy you several minutes before your resources get overwhelmed completely. This time can be crucial to keeping your services online during a DDoS attack.

Call Your Hosting Provider or ISP

Sometimes, you don’t have to handle the attack on your own. Call your ISP or hosting provider and let them know that you’re under attack and ask for their help. Keep their emergency contact information readily available to ensure that you can reach them quickly. In some cases, if the attack is large enough, your ISP might have detected the attack already.

In withstanding a DDoS attack, you stand a chance if the web server is in the hosting center instead of you running it yourself.

The reason being that the data center is likely to have a higher bandwidth and higher capacity routers when compared to your company. Moreover, its employees likely have more experience in dealing with such attacks.

Furthermore, when the web server is located with the host, the host can keep the DDoS traffic aimed at the web server off of the corporate LAN, meaning that some parts of the business will typically be able to continue operating during the attack.

If the DDoS attack is large the host may send the traffic to a dead end. This will allow the attackers to continue their attack, but it’ll fail to take down any of your operations. This could potentially keep the attackers from altering their attack to affect the rest of your business since it will appear as though the attack is still occurring on their end.

Create a DDoS Attack Playbook

A woman using a DDoS attack circle

Creating a playbook is arguably the best way to ensure that you act quickly to a DDoS attack. A playbook documents every step of the pre-planned response whenever a DDoS attack is detected.

The playbook should include all the actions in detail with contact information for all parties that can help. Another significant part of the planned response is how to communicate it to the customers.

Call a Specialist

In case of massive attacks, you may require a DDoS specialist mitigation company to help you stay online. They’re the type of organizations with large-scale infrastructure as well as a variety of technologies available like data scrubbing.

Unfortunately, these DDoS mitigation servers aren’t free. You’ll need to pay for their services, but it may still be economically beneficial to do so if the potential for lost revenue as a result of the attack is significant.

Take the Hit and Wait

DDoS attack keyboard

DDoS attacks typically don’t steal anything from their victims but the losses could still be high. You may not want to go the hard way of calling your ISP or having to hire a DDoS professional. You may also be in a situation where the loss isn’t enough to justify spending money to stop the attack.

In that case, you may just want to wait out the attack. They typically only last for a day or two, so you can just wait it out if you’d like. You could use the time to plan how you’ll announce the attack to your customers and to make a plan for how you’ll handle another attack if it happens again.

Practices To Prevent DDoS Attacks

There’s no denying that DDoS attacks won’t be stopping any time soon. In fact, they keep growing in frequency and intensity. Early detection is crucial to stopping such attacks. Other vital practices to stopping these attacks include the following:

Secure the Network Infrastructure

To mitigate network security threats, you need multi-level protection strategies. This includes advanced intrusion prevention as well as management systems that combine VPNs, firewalls, content filtering, anti-spam, load balancing and several other DDoS defense techniques. These help to identify possible traffic inconsistencies with the highest precision level to block the attack.

Pro Tip:

Also, ensure that your system is up to date, given that outdated methods are the most vulnerable. Therefore, by regularly installing new software and patching your infrastructure, you can close all the attackers’ loopholes.

Observe Strong Network Architecture

Another crucial aspect of security is maintaining secure network architecture. A business should make sure to create redundant network resources. That way, if a server is attacked, another server can take care of the extra network traffic.

Whenever possible, servers should be in various places geographically. This is vital since spread out resources are almost impossible to attack.

Understand Warning Signs

DDoS attack alert with an orange sign

The best way to stay ahead of a DDoS attack is identifying it early. Therefore, it’s vital to understand the DDoS warning signs.

For instance, symptoms such as network slowdown, intermittent website shutdowns and spotty connectivity should raise red flags. No network is perfect, but when the traffic appears to be greater than it should be, then the system is most likely experiencing a DDoS attack and action should be taken immediately.

Leverage the Cloud

There are several advantages of outsourcing DDoS attack prevention to cloud-based services. For instance, the cloud offers more bandwidth and more resources than private networks. Given the ever-increasing number of DDoS attacks, relying entirely on on-premises hardware could fail.

Secondly, the cloud has a nature that makes it a diffuse resource. Cloud-based apps have the capacity to absorb malicious or harmful traffic before it reaches the intended destination. Another advantage is that cloud-based services are usually operated by software engineers who are constantly monitoring the web for new DDoS tactics.

Therefore, using a hybrid environment for applications and data could be the most convenient way to achieve an excellent balance between flexibility and security.

DDoS Protection as a Service

DDoS attack person using a tablet

When looking to prevent DDoS attacks, you should consider third part DDoS protection as it provides increased flexibility for environments combining third party and in-house resources or dedicated and cloud server hosting.

Also, it ensures that security components are of the highest standards and compliance requirements. Its tailor-made security is the main benefit of the model that takes DDoS protection to the next level for any business size.

Are DDoS Attacks Illegal?

For a website owner, there may be nothing worse than being caught on the receiving end of a DDoS attack. Hackers can clog up a site and prevent legitimate users from reaching it, potentially causing huge revenue losses. But the question is: are DDoS attacks illegal?

If you participate in a DDoS attack, you might receive a fine, a prison sentence or both. Therefore, it’s illegal to intentionally impair a computer’s operations or hinder access to data without authorization. This is because DDoS attacks, as well as the use of booter or stresser services, can result in significant harm to businesses, organizations and individuals.


DDoS attack with a red lock on it

The success of your business can largely depend on how you protect it from DDoS attacks, especially in the current technological era.

Therefore, it’s crucial to have a network and data team readily available that fully understands everything about DDoS attacks. Preparation is key to ensuring that your website stays online and that no legitimate customers are denied service.

Ali Qamar Ali Qamar is a seasoned blogger and loves keeping a keen eye on the future of tech. He is a geek. He is a privacy enthusiast and advocate. He is crazy (and competent) about internet security, digital finance, and technology. Ali is the founder of PrivacySavvy and an aspiring entrepreneur.
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