DoS and DDoS Attacks Basic Facts

DoS And DDoS Attacks Basic Facts

DoS And DDoS

What is DoS (Denial-of-Service) attack?

Denial‐of‐service (DoS) attacks are one of the major security challenges in developing cloud computing models. DoS is a security threat that occurs when an attacker prevents appropriate users from accessing specific devices, computer systems, or other IT resources in the cloud.

The major focus of any DoS attack is to overload the capacity of a targeted machine, which ultimately results in denial-of-service (DoS) to the additional requests.

DoS attacks are simple but successful and can cause extreme damage to the cloud resources and services, and often they target the computer networks’ bandwidth or connectivity. With one attack, an organization’s cloud security can be affected for days or even weeks, and the servers could become unavailable to other devices and users throughout the network.

In this type of cyber-attack, a malicious factor aims to make a computer or other specified devices unavailable to its intended users by interrupting its normal functioning. Attackers mostly target government agencies, e-commerce websites, financial websites, etc., to take benefit.

What is a DDoS (Distributed Denial of Service) attack?

DoS And DDoS

A “DDoS” (Distributed Denial of Service) attack is conducted by hackers to disable active domains like Google, MSN, Amazon, Hospital Servers, and many other Enterprise Domains. This is done by sending out a bot, which embeds itself into unsecured computers across the web. This can be millions of bots, depending upon the number of people who have not secured their desktops, laptops, tablets, and other media with proper security suites.

What is the difference between DoS (Denial-of-Service) and DDoS (Distributed Denial of Service)?

DoS can be performed by a single or many computers, using automated tools that generate a huge number of connection requests to a certain website (more than the server can handle). This causes the server to crash because it can’t accept any more connections (it’s called DENIAL OF SERVICE because a server is a computer that renders a service, such as an email, web, print, proxy, etc., and this attack makes it impossible for the service to be supplied) until the problem is solved.

DDoS, on the other hand, is performed by compromising a large number of computers and organizing them in a network (botnet). Botnets are remotely coordinated and controlled by hackers with command-and-control servers or RATs (Remote Administration Tools).

DDoS attacks get launched by several computers simultaneously, so they can be more disruptive than DoS can. They can take down servers for a long time. It’s distributed because the computing power necessary for the attack is distributed over numerous computers organized in a botnet.

So, in a nutshell, DoS utilizes a single connection, while a DDoS attack utilizes many sources of traffic to execute the attack.

DoS and DDoS attacks can be divided into three types:

Volume Based Attacks

Includes UDP floods, ICMP floods, and other spoofed-packet floods. The attack’s goal is to saturate the bandwidth of the attacked site, and magnitude is measured in bits per second (Bps).

Protocol Attacks

Includes SYN floods, fragmented packet attacks, Ping of Death, Smurf DDoS, and more. This type of attack consumes existing server resources, or those of intermediate communication equipment, such as firewalls and load balancers, and is measured in packets per second (Pps).

Application Layer Attacks

Includes low-and-slow attacks, GET/POST floods, attacks that target Apache, Windows or OpenBSD vulnerabilities, and more. Comprised of seemingly legitimate and innocent requests, the goal of these attacks is to crash the webserver, and the magnitude is measured in Requests per second (Rps).

DDoS Attack Types

DoS And DDoS

Smurf Attack

A smurf attack is an amplification attack that is based on Internet Control Message Protocol (ICMP). It is sending a large number of packets with spoofed source addresses; the source address is the victim’s address.

Ping of Death (POD)

Ping of Death is a DDoS attack in which the attacker attempts to crash, destabilize, or freeze the targeted computer or service by sending malformed or oversized packets using a simple ping command.

TCP Syn Flood

TCP Syn Flood is a form of denial-of-service attack that makes the victim server run out of its CPU resources. The attacker sends a succession of SYN requests to the target’s system to consume enough server resources to make unresponsive to legitimate traffic.

UDP Flood

UDP Flood is almost similar to the ping of death but not based on ICMP, rather UDP packets sent in large-sized. The goal of the attack is to flood random ports on a remote host.

ICMP (Ping) Flood

Similar in principle to the UDP flood attack, an ICMP flood overwhelms the target resource with ICMP Echo Request (ping) packets, generally sending packets as fast as possible without waiting for replies. This type of attack can consume both outgoing and incoming bandwidth, resulting in a significant overall system slowdown.


Slowloris is a type of denial of service attack tool which allows a single machine to take down another machine’s web server with minimal bandwidth and side effects on unrelated services and ports. Slowloris is a highly-targeted attack, enabling one webserver to take down another server, without affecting other services or ports on the target network. It does this by holding as many connections to the target web server open for as long as possible.

HTTP Flood

HTTP Flood is a type of Distributed Denial of Service attack in which the attacker manipulates HTTP and POST unwanted requests to attack a web server or application. HTTP floods do not use malformed packets, spoofing, or reflection techniques, and require less bandwidth than other attacks to bring down the targeted site or server.

NTP Amplification

NTP amplification is a type of Distributed Denial of Service (DDoS) attack in which the attacker exploits publically-accessible Network Time Protocol (NTP) servers to overwhelm the targeted with User Datagram Protocol (UDP) traffic.

How to Identify DDoS attack

DoS And DDoS

The most noticeable indication of a DDoS attack is a site or service suddenly becoming slow or unavailable. Of course, there may have legitimate reasons like an instant spike in real traffic, server issues, etc.

Some other signs of a DDoS attack may include:

  • Huge amounts of traffic originating from a single IP address or IP range
  • Increase in bounce rate on a specific page or the whole website.
  • A flood of traffic from users who share a single behavioral profile, such as device type, geolocation, IP address, or web browser version.
  • Unusual traffic patterns such as spikes at odd hours of the day or in every alternate hour.

How to Prevent DDoS Attacks?

DoS And DDoS

Here are some methods to prevent these attacks from impacting your business.

  • Develop a DDoS prevention plan based on a thorough security assessment.
  • Secure your Network Infrastructure with multi-level protection
  • Focusing on a secure network architecture
  • Configure your network hardware against DDoS attacks
  • Consistently monitor the website traffic
  • Activate country blocking
  • Protect your DNS servers
  • Pay attention to connected devices.
  • Ensure you have extra bandwidth
  • Set up a secured VPS hosting
  • Drop packets from apparent sources of attack
  • Purchase a dedicated server
  • Set up RST cookies
  • Install patches and updates frequently


DoS And DDoS

A distributed denial of service (DDoS) attack is when an attacker, or attackers, attempt to make it impossible for a service to be delivered. This can be achieved by thwarting access to virtually anything: servers, devices, services, networks, applications, and even specific transactions within applications. In a DoS attack, it’s one system that is sending the malicious data or requests; a DDoS attack comes from multiple systems.

Generally, these attacks work by drowning a system with requests for data. This could be sending a web server so many requests to serve a page that it crashes under the demand, or it could be a database being hit with a high volume of queries. The result is available internet bandwidth, CPU, and RAM capacity becomes overwhelmed.

The impact could range from a minor annoyance from disrupted services to experiencing entire websites, applications, or even entire business is taken offline.

The objective of a DDoS attack is to prevent legitimate users from accessing your website. For a DDoS attack to be successful, the attacker needs to send more requests than the victim server can handle. Another way a successful attack occurs is when the attacker sends bogus requests.

Detecting a DoS is about as easy as realizing your bandwidth is more restricted than usual. Upon further investigation, you could see that the “users” attempting to connect are not acting like normal users, but as bots with the sole intent of clogging up bandwidth.

The easiest solution to a DDoS is to increase your bandwidth through a service such as Cloudflare. If you cannot handle the DoS attack, ISP’s have been known to drop your traffic until the source stops the attack.

In the grand scheme of things, DoS attacks are one of the less eloquent attack methods and should be looked upon as a “low blow.”

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