What are Denial of Service Attacks & Prevention Techniques?

Written By Sambita Panigrahy  
Anuraag Singh
Approved By Anuraag Singh 
Published On November 8th, 2023
Reading Time 8 Minutes Reading

In order to prevent the targeted users from using a computer system or network, Denial of Service attacks or DoS attacks attempts to bring it down. DoS attacks accomplish this by flooding the victim’s system with too much traffic or information, which results in a crash. In all cases, the attack inhibits legitimate users (such as staff members, members, or account holders) from using the service or resource they intended.

DoS attacks commonly target well-known corporations’ web servers, including those of media, financial, and commercial businesses as well as governmental and commercial institutions. Even though these attacks typically do not result in the theft or loss of crucial data or other assets, dealing with them can nonetheless be very time- and money-consuming for the victim.

Background Information About Denial of Service Attack

As far as the history of the DoS attack witnessed, an SYN flood assault on the ISP Panix was the first of all. Before they were restarted, their services were unavailable for several days.

In 2016, a significant hack targeted the DNS service provider Dyn. Tens of millions of IP addresses were utilized by the Mirai botnet to conduct DNS lookup requests, disabling and interrupting service for popular websites like The New York Times, Reddit, Amazon, Visa, Paypal, and others.

The 2018 2.3 Tbps attack on AWS Shield was the biggest DDoS attack to date.

General Methods of DoS Attacks – Know How Hackers Execute the Attack

DoS assaults usually take one of two routes: they either flood services or crash services. Flood assaults happen when the server cannot handle the amount of traffic coming into the system, which causes it to sluggishly and eventually cease. Common flood assaults are:

  • Buffer Overflow: This is the most frequent Denial of Service attack. The idea of this attack is to transmit more traffic to a network address than the system’s design allows for. It consists of the following attacks in addition to others that are intended to take advantage of flaws unique to particular programs or networks.
  • ICMP Flood: This attack takes advantage of improperly configured network devices by sending phony packets that ping every computer on the targeted network rather than just one specific machine. The network subsequently amplifies the traffic. Some names for this attack include the Smurf attack and the ping of death.
  • SYN Flood: Hacker sends a request to connect to a server using the SYN flood technique, but never completes the handshake. Continues until all open ports are fully utilized by requests and none are accessible to authorized users.

Other denial-of-service (DoS) attacks only rely on bugs that cause the target system or service to fail. The input used in these attacks causes the target system to crash or become extremely unstable, making it difficult to access or use the system.

There is another type of DoS attack present. It’s called distributed denial of service or DDoS attacks. Let’s explore this in detail.

More About Distributed DoS Attacks

As mentioned earlier, the Distributed Denial of Service (DDoS) assault is another sort of DoS attack. A DDoS attack occurs when multiple systems coordinate a synchronized DoS attack on a single target. The primary difference is that numerous sites instead of simply one simultaneously attack the target. The spread of hosts that constitutes a DDoS offers the attacker a number of benefits:

  • He can launch a very disruptive attack with the more powerful machine.
  • Due to the random distribution of the assaulting systems, the attack’s location is impossible to determine. 
  • Multiple machines must be shut down simultaneously, making it more difficult to identify genuine attackers because they are hidden behind numerous systems.

Understand The Difference Between DoS & DDoS Attacks

A Denial of Service assault only employs a few (perhaps one) attacking systems to overwhelm the target. In the early years of the Internet, when services were relatively small in scope and security technology was in its infancy, this was the most prevalent kind of assault. Today, a straightforward DoS assault is frequently simple to avoid because it is simple to spot and stop the attacker. Industrial control systems may be an important exception to this rule because their equipment may be less tolerant to fake traffic or may be connected via low-bandwidth lines that are susceptible to saturation.

Whereas in a distributed denial of service attack, the attacker recruits the assistance of (many) thousands of Internet users to produce a tiny number of requests from each of them that, when added together, overwhelm the target. These participants could be maliciously infected victims or willing accomplices (such as in attacks carried out by loosely organized illegal “hacktivist” organizations).

How Can You Detect Denial of Service Attacks?

Some characteristics may be a clue that an attack is in progress, even if it might be difficult to tell attacks apart from other network connectivity problems or excessive bandwidth utilization.

DoS attack warning signs include:

  • Network performance that is unusually slow, such as a website or file taking a long time to load
  • Your web property or another specialized website is not loading
  • Sudden loss of connectivity for connected devices on the same network

Now, let’s cover how attackers launch these types of attacks.


The goal of a DoS assault is to overload a target server’s bandwidth by using one Internet connection and one device to deliver many, continuous requests to the server. DoS attacks exploit a system software fault to completely consume the server’s RAM or CPU.

By installing a firewall with allow/deny rules, the harm a DoS attack causes in terms of service interruption can be repaired in a short amount of time. A DoS attack only has one IP address, so it is simple to identify the IP address and block future access using a firewall. 

Refer to the below image to see how the DoS attack is carried out.

denial of service attacks

How Can You Protect Against Denial of Service Attacks?

DDoS attacks can still pose a severe threat, even though DoS attacks are easier to resist or prevent.

  • To avoid spoofing, make sure that the source address of the traffic matches the list of addresses for the claimed site of origin. You can also use filters to prevent spoofing on dial-up connections.
  • Limit broadcasting: Attacks frequently send out requests to all the devices connected to the network, which amplifies the attack. Attacks can be prevented by limiting or disabling broadcast forwarding whenever it is possible. Where possible, users can also turn off the echo and charge services.
  • Streamline incident response: When DoS assaults are discovered, your security team may react swiftly by streamlining incident response.
  • Ensure that all endpoints are patched to get rid of known vulnerabilities to protect endpoints. EDR agents should be installed on endpoints that can run them.
  • Firewall configuration: Make that your firewalls are, whenever possible, limiting entry and egress traffic across the perimeter.
  • Watch the network: You’ll be able to detect the beginning of a DDoS assault more quickly if you are familiar with the appearance of typical inbound traffic. Using machine learning to maintain a profile of how your network should look, real-time visibility with network detection and response (NDR) is an effective and dependable technique to spot unusual surges right away.

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Q- What is DoS attack?

An attempt to stop a computer system, network, or service from operating by flooding it with so much traffic that it becomes unusable or slows down is known as a DoS attack.

Q- Why do attackers initiate denial-of-service attacks?

Anger, financial gain, political or ideological agendas, or just plain upsetting others are some of the reasons why attackers may act as they do. Networks, online services, and websites can all be brought down by DoS assaults.

Q- How do DoS attacks operate?

Attackers using denial-of-service techniques flood a target’s system with too many requests or traffic. The target’s software or hardware weaknesses can be exploited, or a network can be overloaded with traffic, to achieve this.

Q- What happens if a DoS assault is successful?

A successful denial-of-service (DoS) attack has the potential to make a website or service unavailable, which could cause financial loss, harm to one’s reputation, and unhappiness among users. It might occasionally also interfere with vital infrastructure.

Q- What defenses are there against DoS attacks?

Firewalls, intrusion detection systems, and content delivery networks (CDNs) are a few examples of preventive measures. Furthermore, rate limitation and load balance can lessen the effects of DoS assaults.