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DrUg_Tit0
e^(i*pi)+1=0

Registered: Nov 2002
Location: Zagreb, Croatia
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| quote: | Originally posted by Fir3start3r
I actually I was reading in some other forums that the DDOS attacks are not a good idea at the moment; Iranians are having enough problems with getting information out of their own country without having to fight for bandwidth from DDOS attacks from the outside.
In short; don't do it please!! |
Yes, I've read that too, but I think it's either gov't propaganda or accidental misinformation. DoS doesn't take much bandwidth, it just opens a huge amount of ports on a server. You see, to exchange info, two computers must agree on which port they'll exchange it over. Basically one computer tells another it wants to connect, the other one says ok and gives back the port number to which the first computer attaches. Overall that's some 20-30 bytes in each direction. After that, information exchange between computers can begin, and while it lasts no other computer can connect to that port.
Now, there is a maximum number of 65535 ports available on any server. When you open a port, the server waits until you start sending data (default value is 60 seconds). If no data has been send during that timeout, server concludes that there's been an error and closes the port to make it available to other users. Now, since you can generally open several hundred ports per second, that means it will take you about a couple of minutes to open up all 65535 ports. When that happens the server starts refusing connections because there aren't any ports available to make one, even though it has plenty of bandwith available. Whenever a port closes, you just ask the server to reopen it again. Occasionally, another user will get through if he manages to ask for the port to reopen before you do so it's not a 100% blockade, but more than 99% of users will not be able to connect.
The only downside to this is that the site comes back online about a minute after the attack stops. So the only way to keep it down is to constantly have someone opening up those ports ports. Total bandwith required to do so is just several kb/s. You can basically bring down a big server with a 56k modem that way.
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1+1=10
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Jun-26-2009 11:26
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Krypton
83.798 g/6.022x10^23

Registered: Nov 2003
Location: Texas
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Jun-27-2009 07:03
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