How a 'denial of service' attack works

First, it was Yahoo.

Then Buy.com, on the day the discount e-tailer went public. One by one, leading sites on the Web have been brought to their knees by so-called denial of service attacks. Such attacks flood a Web server with false requests for information, overwhelming the system and ultimately crashing it. The following graphics explain how such attacks work and how companies can possibly prevent them.

 
How a "denial of service" attack works

In a typical connection, the user sends a message asking the server to authenticate it. The server returns the authentication approval to the user. The user acknowledges this approval and then is allowed onto the server.

In a denial of service attack, the user sends several authentication requests to the server, filling it up. All requests have false return addresses, so the server can't find the user when it tries to send the authentication approval. The server waits, sometimes more than a minute, before closing the connection. When it does close the connection, the attacker sends a new batch of forged requests, and the process begins again--tying up the service indefinitely.

Typical connection

"Denial of service" attack

 
How to block a "denial of service" attack

One of the more common methods of blocking a "denial of service" attack is to set up a filter, or "sniffer," on a network before a stream of information reaches a site's Web servers. The filter can look for attacks by noticing patterns or identifiers contained in the information. If a pattern comes in frequently, the filter can be instructed to block messages containing that pattern, protecting the Web servers from having their lines tied up.

aucune

my english is terrible

[newerawisp]

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The present system of delivering the Internet service is riddled with problems. Denial of service attack is only one prooblem that can't be hidden by the multinational Companies that become a victim of such attack. But the multinational companies will hide the defects in their products or the software that powers their products that could make it possible for hackers to wage such DDOS attacks. Only to-day (July 27, 2005) at the Black Hat Confrence in Las Vegas the Cisco researcher (Michael Lynn) talked about the security flaws in the software powering the Cisco routers and was fired and was served with a restraining order preventing him from talking about the flaw. This is very irresponsible of CISCO. I'll ask every reader of these comments to write to the Cisco CEO John T Chambers to protest the firing and restraining of Michael Lynn asking him not only to hire back Michael Lynn and to vacate the restraining order against Michael Lynn.
The address of Cisco is 170 West Tasman Dr. San Jose, CA 95134-1706
It is important for people to realize that they don't have to put up with the obsolete method of surfing the net. The time has come to develop the server based method of surfing the net as described at NEW ERA WISP that would make DDOS a thing of the Past and people would not have to put up with the silencing of their employees by multinationals like Cisco.

[newerawisp]

NO NEED TO PUT UP WITH DDOS

The present system of delivering the Internet service is riddled with problems. Denial of service attack is only one prooblem that can't be hidden by the multinational Companies that become a victim of such attack. But the multinational companies will hide the defects in their products or the software that powers their products that could make it possible for hackers to wage such DDOS attacks. Only to-day (July 27, 2005) at the Black Hat Confrence in Las Vegas the Cisco researcher (Michael Lynn) talked about the security flaws in the software powering the Cisco routers and was fired and was served with a restraining order preventing him from talking about the flaw. This is very irresponsible of CISCO. I'll ask every reader of these comments to write to the Cisco CEO John T Chambers to protest the firing and restraining of Michael Lynn asking him not only to hire back Michael Lynn and to vacate the restraining order against Michael Lynn.
The address of Cisco is 170 West Tasman Dr. San Jose, CA 95134-1706
It is important for people to realize that they don't have to put up with the obsolete method of surfing the net. The time has come to develop the server based method of surfing the net as described at NEW ERA WISP that would make DDOS a thing of the Past and people would not have to put up with the silencing of their employees by multinationals like Cisco.