What is Denial Of Service – DDoS?
A Denial of Service (DDoS or Denial of Service attack or DoS attack) is an attack on a computer server that results in an inability for the server to respond to requests from its customers.
DoS, written with a capital letter in the first and third place, is the symbol of denial of service, literally a denial of service. In this type of attack tries to bring the operation of a computer system that provides a service, such as a website, at the limits of performance, working on one of the input parameters so that it becomes no longer able to deliver the service.
A denial of service is a situation where a server computer is unable to meet its customers’ requests. A server computer (e.g., Web server) needs to handle multiple requests in a short period of time. When the server is unable to process all the requests it receives, there is denial of service.
An attack by distributed denial of service (in English, distributed denial of service attack or DDoS attack) is a Denial of service in which the target server is attacked by several computers simultaneously.
The DDoS attacks are usually carried out by sending many packets of requests, usually a Web server, FTP or e-mail saturating the resources and making the system “unstable”, so any system connected to the Internet and providing network services based on TCP subject to the risk of DoS attacks. Initially, this attack was carried out by the “cracker” as a gesture of dissent against the ethical commercial websites and institutions.
Today DoS attacks have the connotation decidedly more “criminal” to prevent network users access to Web sites the victims of the attack. To make more effective the attack usually uses many computers on which it was previously unaware inoculated a program specially created to DoS attacks and that activates a command from the cracker maker. If the malicious program has spread to many computers, it may be that thousands of PCs violated by a cracker, and unwittingly produce the same moment an unstoppable stream of data like an avalanche that overwhelms even the most capacious link target site.
Not only the server systems may be victims of a DoS attack, but also simple users and clients, as the case of DoS attack to iPhone.
The chance to meet ever-smaller systems vulnerable really meant that DoS attacks have declined more strikingly, however, it was discovered extreme vulnerability of the network for increasing processing power of current personal computer business and the public Internet via DNS systems.
The implementation of TCP / IP, which does not guarantee as security on the identification of senders of packets but will protect the anonymity, can be used to mask the true origin.
Since apparently legitimate connections, it is impossible to stop without even interrupting the flow actually harmless. But drastically reducing the number of sessions open simultaneously the impact of the attack is reduced significantly without restricting the flow of regular packets.
Even limiting the conversation to the blocking of a website, do exist and have been used several ways to achieve this result.
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