RE: detecting promiscuous 802.11x cards...

"David Huseby" <[email protected]>
Newsgroups gmane.network.wireless.seattle.general
Message-ID <[email protected]>
-]  Code to steal:
-]  http://www.cmpe.boun.edu.tr/~tas/
-]  
-]  documentation:
-]  http://www.securityfriday.com/promiscuous_detection_01.pdf


Thanks.  The detection method takes advantage of the difference between
the hardware filter in the nic and software filter in the
(Linux/Windows) kernels.  By sending a packet that would normally get
blocked by the hardware filter (when not in promiscuous mode) but
accepted by the software filter we can then assume that all hosts that
reply are in promiscuous mode.  Unless the Linux kernel has been changed
since 2001 to replicate the full hardware filter when a nic is in
promiscuous mode, this kind of detection should still work...and work
with 802.11 nics as well.

Hrm...does anybody know if the Linux kernel has gained some
modifications that prevent the kernel from responding to ARP messages
with group bits set when the source device is in promiscuous mode?  If
not, I smell a patch coming...  That way I could sniff and detect
promiscuous nodes without being detected myself.

I wonder if IPTABLEs and the kernel can be made to work together to dump
detection ARP packets into a LOG target so that I can log if anybody is
scanning for promiscuous mode NICs?  Interesting...

Dave
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