Hello everyone,
One of the coolest yet still relatively obscure features of Nmap is
the Idle scan (-sI). Not only does this allow for a completely blind
portscan (no packets sent to the target from your real IP), but it can
even allow you to bypass packet filters in certain circumstances. I
think one reason this has not taken off is that documentation is
pretty scarce. So I have written an informal paper describing Idle
scanning as well as several other exploits based on predictable IPID
sequence numbers. It includes real-life examples as well as a section
on defending yourself from these techniques. The paper is at
http://www.insecure.org/nmap/idlescan.html and feedback is welcome.
If you want to test Idle scanning functionality, I recommend Nmap
3.10ALPHA3 (released an hour ago) as it fixes several bugs and
improves the algorithm slightly.
Cheers,
Fyodor
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Received on Sep 16 2002
Intro
