RE: V/Scan for Wireless LANs
From: Bartholomew, Brian J (BartholomewBJ_at_state.gov)
Date: 07/21/03
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To: "'Ian Chilvers'" <Ian.Chilvers@prolateral.com>, "'pen-test@securityfocus.com'" <pen-test@securityfocus.com> Date: Mon, 21 Jul 2003 10:47:52 -0400
I have successfully cracked 40 and 104 bit WEP keys with reinj.c and
Airsnort or Kismet. Just use Airsnort or Kismet to listen and store the
"interesting" traffic, and reinj.c to create it. One usually needs between
100 MB to 1 GB of traffic to crack the key, but once the data is captured,
the key cracks in a matter of seconds.
There is a good paper that describes the weak implementation of
initialization vectors entitled "Weaknesses in the Key Scheduling Algorithm
of RC4" by Scott Fluhrer, Itsik Mantin, and Adi Shamir. I suggest reading
it.
I mentioned Kismet above. It is one of the best tools out there for
WLAN testing. It allows you to perform a variety of things to the AP such
as spoofing, disassociations, capture traffic, sniff out "hidden" APs, etc.
It is all around a better tool to use than NetStumbler since it detects APs
passively, instead of broadcasting everywhere. It even detects other
NetStumbler clients.
The suggestion to brute force the key is not a good idea since, as
one person already pointed out, it would take a very long time to BF it. It
could be done I guess, but by the time the key is cracked, they would have
probably already changed it.
Personally I think the best way of attack is to use some sort of man
in the middle attack. If you are able to disassociate the clients from that
AP and have them re-associate with you, you are golden :).
Brian J. Bartholomew
U.S. Dept of State, Bureau of Diplomatic Security
Computer Incident Response Team
(202)663-2304
-----Original Message-----
From: Ian Chilvers [mailto:Ian.Chilvers@prolateral.com]
Sent: Friday, July 18, 2003 12:45 PM
To: pen-test@securityfocus.com
Subject: V/Scan for Wireless LANs
Hi all
We've been asked to perform a vulnerability assessment for a company that
has a Wireless LAN. The W/LAN is running WEP with a random key generated,
rather than a dictionary word.
Are there any tools out there that can brute force a WEP.
Take this example. A person parks the car in the car park and sniffs the
air waves with a product like NetStumbler. He discovers the W/LAN but with
WEP.
Is there a tool he can use to discover the WEP key (possible by brute force)
If there isn't such a tool, how does this sound for an idea.
Run a app that starts at binary 0's and counts upto 128bits of 1's
For each sequence listen to see if there are any sensible packets or even
send out a DHCP discover request to see if you get a reply. This would then
possibly give you the WEP key.
Any comments
Ian....
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