What are DOS and DDOS attacks?

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DOS or DDOS attacks are related to internet and networks. DOS stands for “Denial of Service” and DDOS stands for “Distributed Denial of Service”. In a DOS or DDOS attack the attacker attempts to prevent the authentic users from accessing the the web services. In both of these attacks the attackers tries to block the services by overloading the targeted server where the web service is running.


Overview: When ever you try to access any website you send http requests to the server where the website is being hosted. All the webserver and the networks are capable of handling a particular number of request per second (threshold value) if the number of requests crosses this threshold value then the webserver goes into a non active mode where it will no more be able to handle any http requests. At this condition the webserver virtually dies. This situation is called denial of service. Before making a website live, the number of users are estimated and accordingly the hosting capacity is selected. Hence all website has got their own limit.


How does DOS and DDOS attack work? In DOS attack the attacker runs a program on a system connected to internet. This program sends multiple http requests to the targeted server causing network blocking for the web server. There after the authentic users will not be able to access the website any more. When you try to open any website under DOS or DDOS attack you will get a network timeout error in your browser.


What is the difference DOS and DDOS attack?


In both the attacks the targeted server and network goes down. So what is the difference between these two attacks. Actually these two attacks are named based on the source of attack. In DOS attack the attacker runs the program from a single computer where as in DDOS attack the attacking program are being run from multiple systems or from a distributed network.In DDOS attack the attacker may use your system to attack a different system. See the below image description for a clear understanding of DOS and DDOS attacks:


DOS Attack:




DDOS Attack:




Symptoms of Attack:


* Unusually slow network connection

* Unable to access any website

* Unavailability of a website without any reason

* Dramatically increase in the request that a server receives


In my upcoming posts I will give some tips to prevent DOS and DDOS attack


+Ayodhyanath Guru holds a B.Tech degree in Electrical Engineering and has worked with various prestigious clients in the IT industry and presently working as a Software Engineer. He is a part time blogger and presently authors the Jafaloo.Com blog. Being a tech enthusiast Guru likes to surf the web and blogs about interesting technical topics like How-To guides, freewares, Tutorials, Software, Gadgets, web applications etc. Apart from blogging he likes coding in Java/J2EE and PHP.

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