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Imagine that I have to pentest a server that implements portscan detection based on the number of packets received to different ports in a time interval.

I don't know that the server is implementing this protection, I don't want my IP to be blocked and I want to be as fast as possible without being blocked.

How can I detect that the server is implementing this protection? Can I estimate the threshold where my IP will be blocked?

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up vote 3 down vote accepted

Logically you cannot know at which point the server will block you until you actually reach the threshold and be blocked. This is not something that the server will advertise.

If you have a spare IP, you can increase the number of packets per second until you are blocked, at which point you know what threshold not to cross with your other IP.

Good firewalls are likely to use more complex heuristics, depending not only on the number of packets but also the target ports. Chances are that you can work out the actual firewall heuristics by burning a few IP, but you cannot guess it a priori.

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Do you know any tool to automate this process? I know that with NMap or hping2 I could elaborate a script but I would like to know if already exists any tool. –  kinunt Feb 14 '13 at 11:50
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