1.1 Definition

Denial-of-Service attack, henceforth referred to as DoS attack, is a form of cyber-attack in which, the person attacking (known as the attacker) will prevent you or any legitimate user from accessing services or information.

The attacker will usually attack, either your computer and its associated network or the network and computers of those sites that you try to access for information or services. A successful attack will prevent you from accessing online accounts (online banking, online storage, emails etc.), websites etc. which depend on those computers and networks that are attacked.

1.2 A Quick Example

Let us assume that you are trying to access www.forbes.com. For this, you need to enter the URL into your browser and then the browser will user your network to query for find the website’s server using the URL. Once found, the network will then look up for the webpage in the server computer. The server will then process the request you made and send the data to your web browser through your network and your web browser will show the web page on your computer. The server of Forbes can only process a specified number of request at any given point of time. In a DoS attack, the attacker will send numerous requests to the server computer where the website of Forbes is store. When the server tries to process all those requests, the load on the server increases. Now when you try to access the Forbes website, the server will not be able to process your request because of the overload created by the attacker. Thus, you cannot access the website because the server will deny your request. This is called DoS.

1.3 DDoS

DDoS is called Distributed Denial-of-Service. The DDoS attack takes place when an attacker finds a security weakness on your (or any other user’s) computer and network. The attacker will then take control of your computer and use your computer and your network to send large amounts of data to any website and this will cause overload on the website’s server which will then lead to DoS. This form is called Distributed DoS because the attacker will be using multiple computer (his or her own computer and yours and may be a few others) to launch the attack. Thus, the attack is distributed from several computers and networks instead of just one.

1.4 Prevention of DoS and DDoS

There is no straight forward way to prevent DoS or DDoS. However, the likelihood or the probability of the occurrence of DoS and DDoS can be reduced to a great extent by using the following methods:

• Installing a reputed and trusted anti-virus is important. It also necessary to maintain the anti-virus by properly setting all security measures and ensuring that the web-security features is working.
• Ensuring that firewall of the anti-virus is properly configured and that properly rules have been set for both incoming and outgoing traffic.
• Never distributing your email address randomly and also ensuring that you have set and configured spam filters properly.

Denial-of-Service is one of the most common forms of cyber security issues and it happens frequently. You will need to stay alert to reduce the chances of becoming a victim of this form of cyber-attack.