The term ‘Denial of Service’ (DoS) refers to an attack on the computer systems network that renders the entire network completely unusable for the intended users. There are two kinds of such attacks – Denial of Service and Distributed Denial of Service. Such attacks, basically, overwhelm the computer’s processing capacity and may prevent a user from accessing websites, emails, banking, online accounts and various other services.

Denial of Service

Denial of Service or DoS attacks are not new and they have been around for decades now.

Denial of Service or DoS attacks are not new and they have been around for decades now. Distributed attacks are relatively recent and the first of such kind was witnessed some time in June-July 1999. The first such documented DoS attack occurred in August 1999, when a virus called ‘Trinoo’ was deployed in over 227 systems networked to a single computer at the University of Minnesota. The computer was completely out of use for two days.

While in the past, it has been web hosting computers becoming the target of such attacks; of late, personal computers have also become the victims of such an attack. As these viruses make your system insecure, it is important to defend your system from such attacks.

Here are some ways to prevent such attacks:

• Filtering – It is usually easy to locate and filter DoS attacks. The routers of a system can be deployed to spot and filer DoS connections and, thereby, prevent them from making the network or the server slow.

• Moving – Usually, DOS attacks are pointed at a particular IP address. It is recommended to move the website to another IP address on the same network.

• Blackholing – Blackholing refers to directing all the traffic of a website to another address that does not exist. In this manner, other websites on that server or network are not impacted.

Apart from these methods, there are anti-DOS applications and appliances that have been created to detect and block DOS attacks. Though such attacks do not permanently damage a system, they do cause inconvenience for a few days to the users of the victimised network.

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