Denial of service attack: what it is and how to prevent it

Have you ever felt unusually slow on your network or unexpectedly unavailable for a particular site?Most likely, there could be a denial of service attack . You may be familiar with the term Denial of Service , but in reality it can be difficult to distinguish a real attack from normal network activity. Denial of Service (or DoS) Attackwhich, as the name suggests, is directly related to denial of service, especially on the internet. A DoS attack is a kind of attack that consumes a user’s resources and brings the network to its knees, thereby preventing legitimate users from accessing any website. DoS attack has been and remains one of the most sophisticated attacks for which there is no potential prevention policy. In this post, we will explain what a DoS attack is and how best to prevent it and what to do if you know you have been attacked.


  1. What is DoS or Denial of Service Attack
  • Types of DoS attacks
  1. 1] SYN Flood
  2. 2] HTTP Flood
  3. 3] Distributed Denial of Service (DDoS) Attack
  • Preventing DoS attacks

What is DoS or Denial of Service Attack

In a DoS attack, an attacker with malicious intent prevents users from gaining access to a service. It does this by either targeting your computer and its network connection, or the computers and website network that you are trying to use. Thus, it can deny you access to your email or Internet accounts.

Imagine a situation where you are trying to log into your Internet Banking account for online transactions. However, oddly enough, you are denied access to the bank’s website despite your fast internet connection. Now there can be two possibilities – either your ISP is down or you are undergoing a DoS attack!

In a DoS attack, the attacker sends a stream of unnecessary requests to the main server of the respective website, which basically overloads it and blocks any further requests before the capacity is saved back. This results in the rejection of incoming legitimate requests to this website and, as a result, you are a victim .

However, attack methods can differ depending on the attacker’s motives, but this is the most common way to launch a DoS attack. Other attack methods could include preventing a specific person from accessing a specific website, obstructing the connection between two computers on the server side, hence disrupting the service, etc.

Some attackers also use another type of DoS attack – email bombing , in which a large number of spam emails are generated and sent to the Inbox, which eliminates any further requests to the mail server. This can happen everywhere, even in the e-mail account provided to you by your employer, not to mention the public email services such as Yahoo, Outlook, and so on. D. . You may even lose any additional legitimate emails as your allocated storage quota will be full. With a wide variety of ambitions, attackers’ motivations can range from “just for fun” to financial fraud and revenge.

Types of DoS attacks

Depending on the nature and purpose of the attack, there are several types of programs that can be used to launch DoS attacks on your network. Note the following most commonly used DoS attacks:

1] SYN Flood

SYN Flood takes advantage of the standard way to open a TCP connection. When a client wants to open a TCP connection to an open port on the server, it sends a SYN packet . The server receives the packets, processes them, and then sends back a SYN-ACK packet that includes the source client information stored in the Transmission Control Block (TCB) table . Under normal circumstances, the client sends back an ACK packet confirming the server’s response and therefore opening a TCP connection. However, with a potential SYN attackThe attacker sends a whole bunch of connection requests using a spoofed IP address, which are considered valid requests on the target machine. Subsequently, it processes each of them and tries to open the connection for all these malicious requests.

Under normal circumstances, the client sends back an ACK packet acknowledging the server’s response and therefore opening a TCP connection. However, in a potential SYN attack, the attacker sends a whole bunch of connection requests using a spoofed IP address that the target machine considers valid requests. Subsequently, it processes each of them and tries to open the connection for all these malicious requests. This forces the server to wait for an ACK packet for every connection request, which never actually arrives. These requests quickly populate the server’s TCB table before it can time-out for any connection, and thus any further legitimate connection requests are queued expectations.

2] HTTP Flood

It is most commonly used to attack web services and applications. With little emphasis on high-speed network traffic, this attack sends out complete and seemingly valid HTTP POST requests . Designed specifically to exhaust the resources of the target server, the attacker sends a series of these requests to ensure that the target servers are not processing additional legitimate requests while they are busy processing bogus requests. Still, it’s that simple, but it is very difficult to distinguish these HTTP requests from valid ones, since the content of the Header appears to be valid in both cases.

3] Distributed Denial of Service (DDoS) Attack

A distributed denial of service or DDoS attack is like an officer in this gang. DDoS is greatly complicated by levels above a typical DoS attack, generating traffic to the target machine through more than one machine. An attacker controls several compromised computers and other devices at once and distributes the task of filling the target server with traffic, excessively consuming its resources and bandwidth. An attacker could also use your computer to launch an attack on another computer if there are security issues.

Now, as far as is obvious, a DDoS attack can be much more effective and real than a DoS attack . Some websites that can easily handle multiple connections can be easily shut down by sending multiple concurrent spam requests. Botnets are used to recruit all kinds of vulnerable devices that can be compromised by injecting a virus into them and registering them with a zombie army that an attacker can control and use. for a DDoS attack. Hence, as a regular computer user, you should be aware of the security holes in and around your system, otherwise you may end up doing someone’s dirty work and never know about it.

Preventing DoS attacks

DoS attacks cannot be predetermined. You cannot prevent the victim of a DoS attack. There are not many effective ways to do this. However, you can reduce the likelihood of being part of such an attack, when your computer could be used to attack another. Write down the significant points below that can help you get the odds in your favor.

  1. Deploy antivirusand firewall software on your network if you haven’t already. This helps limit bandwidth usage to only authenticated users.
  2. Server configurationcan help reduce the likelihood of an attack. If you are a network administrator for a company, take a look at your network configuration and tighten your firewall policies to block unauthenticated users from accessing server resources.
  3. Several third-party servicesoffer guidance and protection against DoS attacks. They can be expensive but effective. If you have the capital to deploy these services on your network, better get started.

DoS attacks tend to target large organizations such as banking and finance companies, merchant and commercial cigarette butts, etc. You need to be fully aware and look over your shoulder to prevent any potential attacks. While these attacks are not directly related to theft of confidential information, it can take a significant amount of time and money for victims to get rid of the problem.

by Abdullah Sam
I’m a teacher, researcher and writer. I write about study subjects to improve the learning of college and university students. I write top Quality study notes Mostly, Tech, Games, Education, And Solutions/Tips and Tricks. I am a person who helps students to acquire knowledge, competence or virtue.

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