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Re: Wi[r]eless security (was: Suspend bug)



Les <hlhowell pacbell net> wrote:

On Sun, 2007-02-04 at 11:07 -0700, David G. Miller wrote: Snip!
> Oh yeah. One other thing I do is my AP is in my basement. The basement > walls are concrete with rebar so they do a good job of attenuating the > WiFi signal. Makes it even harder to crack my network on a drive by but > someone on my neighbor's roof would probably still get a decent signal. > > I always like the saying, "Locks keep an honest person honest." To this > I add, "... or divert the dishonest person to look for someone with a > weaker lock."

Hi, Dave,
	Have you confirmed the signal condition from your basement?  The WLAN
signal is very multipath capable, and the receivers for good systems can
pick it out of the mud with only about a 1db SNR.  That is about 10
times as sensitive as most Ham Radios, and about 10000 times more
sensitive than most AM or FM table radios.

	The technology is really amazing.

Regards,
Les H
Actually, it was experimentation while visiting my parents. Turns out that one of their neighbors runs an open AP. I get a good signal to the neighbor's AP when I'm on the main floor of my folk's place but an unusable signal when I'm in their basement. I get the best signal when I'm at the end of their house closest to this neighbor. This is with concrete block foundations and wood frame houses. I don't know where their neighbor has his AP. This also fits with my experience helping some folks get wireless coverage everyplace they wanted it by moving their AP around inside their house (bad AP location: bad coverage with lots of dead spots; good AP location yields minimal dead spots but probably accessible to "others").

I ran into this same effect at my last employer where some of the sales engineers had set up a rogue AP. The steel frame of the office meant that the AP was only accessible from certain locations on the floor we occupied (e.g., not at all when the elevators were between the AP and the person attempting to connect). I also vaguely remember reading an article on suggestions for EM hardening to take advantage of this for securing wireless. I put my experience with the neighbor's wireless together with the strategy described in the article on EM hardening and came up with putting my AP in my basement should make the signal fairly unusable off of my property.

The radio signal used by wireless does a good job of penetrating wood, drywall and most home building materials (no multipath involved). It doesn't do as well with steel, wiring or *enough* earth. This is especially true when the steel forms a "cage" as is the case of rebar in a poured foundation.

Cheers,
Dave

--
Politics, n. Strife of interests masquerading as a contest of principles.
-- Ambrose Bierce


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