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[Ham-80211] Access control suggestions

David Young dyoung at pobox.com
Mon Nov 1 21:50:17 UTC 2004

On Mon, Nov 01, 2004 at 09:31:28AM -0800, Steven Phillips wrote:
> That still leaves one question open.  The AP is still
> being used under part 97 rules.  Is using static IP
> assignments under AMPERNET sufficient access
> restriction?  Part 15 users can still connect to the
> AP, but they will not get any network access and can't
> do anything beyond connecting to the AP.  This is
> because they will not have an IP address.  The only
> exception I can think of is if the general public
> discovers the AMPRNET IP scheme and assigns themselves
> an IP address?  Simple solution.  When a person
> applies for access to the network, require them to
> provide the unique MAC address of their WLAN card(s)
> and do a MAC check during authentication.  If a person
> does spoof an IP, they still won't have access because
> they do not have an authorized MAC address.
> So, there's my $20 worth.  Let me know what you think
> and if you have any thoughts about my suggestions.


MAC authentication is very weak.  One need only eavesdrop on your AP to
find out the authorized MACs.  Ditto IP address authentication.

Keep in mind that for a person to "operate" your Part 97 AP, their
computer needs only to send your AP an 802.11 packet.  Virtually any
802.11 management request (Probe, Authentication, Association) will induce
your AP to send a response.  Also, your AP will probably produce a CTS
response to any RTS packet, regardless the RTS-sender's authentication
status.  Sending your AP a data packet will likewise yield an 802.11 ACK,
or even a Deauthenticate response.  As a matter of course, your Part 97 AP
is going to receive Probe Requests from 802.11 stations that are scanning
for APs.  A clever and malicious person may be able to make your Part
97 AP send a flood of packets all day long, without ever authenticating.


David Young             OJC Technologies
dyoung at ojctech.com      Urbana, IL * (217) 278-3933

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