What is a DoS Attack? Demystifying Denial-of-Service Threats 

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What is a DoS Attack? Demystifying Denial-of-Service Threats 

What is a DoS attack?

Do you want to know about denial of service? Well, it’s a kind of cyber attack technique that adversaries use to take unauthorized access to the resources of the victim from a different POV. A Denial of Service (DoS) attack is a malicious activity that hinders the regular operation of a targeted server, service, or network by flooding it with an excessive volume of illicit traffic or requests, thus leaving it unusable for authorized users. Let’s get deep into the topic!

How does a DoS attack work?

The operation of a Denial of Service (DoS) assault can be summarized as follows:

  1. Target Selection: To cause disruption, the attacker chooses a target system or network. A server, network infrastructure, website, or any other online service could be this.
  2. Resource Depletion: The attacker overwhelms the target with a deluge of requests, data, or traffic. The amount of bandwidth, processing power, and memory used by the target is depleted by this onslaught of communications.
  3. Service Disruption: The target’s inability to reply to users’ valid requests stems from an overload of its resources. As a result, legitimate users experience a denial of service, making it impossible for them to access the targeted service.
  4. Types of Attacks: Different DoS attack types exist, such as:
  1. Volume-based attacks: Like in a Distributed Denial of Service (DDoS) attack, which uses several compromised systems (botnets), to overwhelm the target with an enormous amount of traffic.
  2. Protocol-based attacks: Take advantage of holes in network protocols by starting handshake procedures or keeping connections open to waste resources.
  3. Application layer attacks: Take advantage of holes in web servers or apps by flooding them with requests that will take a lot of processing resources to process.
  1. Impact: Depending on the type of service being targeted and the length of the attack, the consequences of a successful denial-of-service (DoS) attack can range from brief irritation to substantial financial loss.
  2. Detection and Mitigation: Businesses use a range of strategies to identify and stop denial-of-service (DoS) assaults, such as rate-limiting, content delivery networks (CDNs) for traffic distribution, intrusion detection/prevention systems, and traffic filtering.
  3. Legality: DoS attacks are prohibited in most countries and can have serious legal repercussions for those who launch them. They are regarded as a type of cybercrime that carries severe penalties, including jail time.

What are some historically significant DoS Attacks?

S.No. Attacks How?
1. Ping of Death (1996) Used flaws in the Internet Control Message Protocol (ICMP) to send large packets that caused the target systems to crash.
2. Yahoo! DDoS (2000) One of the first well-known DDoS assaults attacked Yahoo! and other well-known websites, causing hours-long service disruptions.
3. Dyn DDoS (2016) Popular websites including Twitter, Netflix, and Reddit experienced severe internet outages and disruptions due to a huge Distributed Denial of Service attack that targeted Dyn, a major DNS provider.
4. GitHub DDoS (2018) One of the biggest DDoS attacks ever recorded, with a peak throughput of 1.35 terabits per second (Tbps), was directed towards the well-known code hosting platform GitHub, causing disruptions to its operations.
5. Mirai Botnet (2016) Mirai, a notorious tool for initiating massive denial-of-service attacks, infected thousands of Internet of Things (IoT) devices, including routers and cameras, to build a potent botnet that was used to assault several targets, including Dyn.

What are common Denial-of-Service Attacks?

  • Distributed Denial of Service (DDoS)

Involves a large number of compromised systems—often Internet of Things devices or malware-infected computers—overwhelming the target’s resources with a large amount of traffic or requests.

  • SYN Flood

Utilizes a lot of SYN requests to establish connections, but doesn’t finish them, using up the target’s resources and blocking valid connections, to take advantage of the TCP handshake process.

  • HTTP Flood

Overloads a web server with HTTP requests, using up all of its processing power and bandwidth and causing a disruption in service or outage.

  • UDP Flood

Bursts the target’s network capacity by sending a lot of User Datagram Protocol (UDP) packets, which causes an interruption.

  • Ping Flood

Sends ICMP Echo Request (ping) packets to the target continuously, overloading its network capacity and causing it to become unresponsive to valid traffic.

  • Slowloris

Sends HTTP headers at regular intervals, keeps connections open for as long as feasible, and eventually uses up all available server resources in an attempt to take advantage of the way web servers handle connections.

  • DNS Amplification

Uses DNS servers that are incorrectly configured to magnify a small number of DNS queries into a barrage of answers aimed at the target, exceeding the network’s capacity.

  • NTP Amplification

Analogous to DNS amplification, except it takes advantage of Network Time Protocol (NTP) servers to produce a deluge of replies, increasing the assaulter’s traffic.

  • Smurf Attack

Sends ICMP Echo Request packets to a network for amplification (like a broadcast address) by spoofing the originating IP address. This causes all of the network’s devices to respond to the spoof address, overloading the intended recipient.

  • Teardrop Attack

Sends overlapping offsets in fragmented IP packets, which when the target system reassembles the packets, causes it to crash or become unstable.

How do you avoid being part of the problem?

S.No. Factors How?
1. Keep Systems Updated Make sure that the most recent security patches are applied to your operating systems, applications, and firmware regularly to minimize vulnerabilities that hackers could use to convert your device into a bot.
2. Use Strong Authentication Make sure all of your account passwords are strong and distinct, and if you can, use multi-factor authentication (MFA) to prevent unwanted access to your devices and accounts.
3. Install Security Software To identify and eliminate any malicious software that can potentially turn your devices into bots taking part in a denial-of-service attack, install reliable antivirus and anti-malware software on them.
4. Enable Firewalls Turn on firewalls on your hardware and network routers to keep an eye on and manage incoming and outgoing traffic. This will stop any unusual behavior that might be linked to a denial-of-service attack.
5. Be Wary of Phishing Be cautious when you click links or open email attachments since phishing efforts might deceive you into downloading malware onto your devices that can be used to initiate or take part in denial-of-service attacks.
6. Monitor Network Activity Keep an eye on your network traffic to spot any odd trends or sudden increases in data consumption that might point to the use of your devices in a denial-of-service assault.
7. Configure IoT Devices Securely To keep your Internet of Things (IoT) devices safe from denial-of-service (DoS) attacks, change the default passwords on them, turn off any unused services, and make sure the firmware is up to date.
8. Educate Yourself Keep yourself updated about the newest dangers to cybersecurity and the best ways to defend your network and devices from denial-of-service (DoS) attacks. Teach your family members and coworkers to do the same.

How Can You Identify a DoS Attack?

The following signs may be used to recognize a denial-of-service attack:

  1. Unusually High Traffic Volume
    Unexpected increases in network traffic that beyond typical patterns may indicate a denial-of-service attack. An appreciable rise in incoming requests or data packets may be one example of this.
  2. Service Degradation or Unavailability
    It may be a sign of a denial-of-service (DoS) attack if users encounter sluggish response times or are unable to access a specific service or website.
  3. Network Congestion
    Another sign of a denial-of-service attack is when network equipment, like switches or routers, is overloaded or experiencing congestion as a result of an influx of traffic.
  4. Unusual Behavior in Network Logs
    Keep an eye out for anomalies in network logs, such as persistent attempts to join from the same IP address, a high number of unsuccessful login attempts, or strange traffic patterns.
  5. Abnormal Resource Consumption
    A DoS attack may be using resources if servers or network devices experience higher CPU or memory utilization without a matching rise in genuine activity.
  6. Ping Sweeps or Port Scans
    Ping sweeps and port scans directed at your network in significant quantities could be signs of reconnaissance being done by attackers getting ready for a denial-of-service attack.
  7. Inability to Access Specific Resources
    DoS attacks that target particular resources, like web pages or network shares, maybe the cause of problems experienced by users who are having trouble accessing those resources.
  8. Unsolicited Traffic from Known Malicious Sources
    Unwanted traffic coming from known malicious IP addresses or ranges could be part of a botnet-launched denial-of-service attack on your network.
  9. Warnings from DDoS Mitigation Services
    It is important to heed warnings or alerts from DDoS mitigation providers regarding anomalous traffic patterns or possible attacks if you have a subscription to these services.
  10. Communication from Internet Service Providers (ISPs)
    If your ISP notices unusual activity coming from your network or any indications that a DoS attack is aimed at your network, they may alert you.

Who and what is this guidance for?

This advice is intended for individuals, companies, and organizations who are worried about defending their servers, networks, and online services against the possibility of Distributed Denial of Service (DDoS) and Denial of Service (DoS) assaults.

In the face of possible attacks, it offers tactics and best practices to reduce disruption risk and preserve digital asset availability.


If you want to know more deeply about Denial-of-Service Attacks, you can get in contact with Craw Security which is a reputed institute offering customized courses for cyber security. One of the best courses Craw Security offers is the Industrial-Oriented Innovative Cyber Security Course in Singapore.

This course is specially designed to offer the best understanding of cyber security topics under the guidance of professionals in cyber security who have worked in the IT Sector for years. With that one will be able to get the facility of a Virtual Lab to get real-life experience.

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Frequently Asked Questions

What is a DoS attack? Demystifying Denial-of-Service Threats

  1. What does a DoS attack do?

A Denial of Service (DoS) attack prevents a network, server, or service from operating normally by flooding it with too many requests or traffic, making it unavailable to authorized users.

2. What is a DDoS attack, for example?

Multiple infected computers flood a target with a massive volume of traffic or requests, exceeding its resources and disrupting service. This technique is known as a distributed denial of service (DDoS) assault.

3. What is a DoS or DDoS attack?

A Distributed Denial of Service (DDoS) attack is a coordinated assault using multiple compromised systems to overwhelm a target with traffic or requests, rendering it inaccessible to authorized users. A Denial of Service (DoS) attack is a malicious attempt to disrupt the availability of a service.

4. What are the four types of DoS attacks?

The four types of DoS attacks are:

  1. Volume-Based Attacks,
  2. Protocol-Based Attacks,
  3. Application Layer Attacks, and
  4. Distributed Reflection Denial of Service (DRDoS).

5. Why do DDoS attacks happen?

DDoS attacks can be carried out for several reasons, such as to create havoc and disruption or for political, financial, competitive, or hacktivism purposes.

6. Is DDoS illegal?

Because DDoS assaults interfere with the regular operation of computer systems and networks without authorization, they are unlawful in the majority of states.

7. Can DDoS crash a server?

Indeed, a server’s resources may be overloaded by a Distributed Denial of Service (DDoS) assault, rendering it unavailable or crashing.

8. Is DDoS malware?

No, distributed denial of service, or DDoS, is not malware in and of itself. Rather, it is a kind of cyberattack in which a target is bombarded with malicious traffic.

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