Completly block signal.

Discussion in 'Wireless Internet' started by John Larsen, Jul 20, 2004.

  1. John Larsen

    John Larsen Guest

    Any suggestions on how to completly block a signal. I have a device
    that I wish to use its ethernet and turn off its wireless (leaving it
    on leaves security problems) but there is no option in its
    configuration to do this. I've removed the antenta and tried covering
    the hole with aluminum wrap, but still got a signal from a good
    distance. I need to have no signal from any distance (or atleast no
    signal from 10 feet away seriously).

    Any suggestions.
     
    John Larsen, Jul 20, 2004
    #1
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  2. John Larsen

    Bill Guest

    if its a laptop, take the wireless card out... or go into the hardware tap
    and disable the wireless card.. when you want to use wireless again, go
    back and enable the card
     
    Bill, Jul 20, 2004
    #2
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  3. :Any suggestions on how to completly block a signal. I have a device
    :that I wish to use its ethernet and turn off its wireless (leaving it
    :eek:n leaves security problems) but there is no option in its
    :configuration to do this. I've removed the antenta and tried covering
    :the hole with aluminum wrap, but still got a signal from a good
    :distance. I need to have no signal from any distance (or atleast no
    :signal from 10 feet away seriously).

    You want Tempest class shielding. Except that you won't be able to
    buy it under that name or even find out what it's specifications are
    unless you are in the military and have a Need To Know.

    What you -can- buy is a Faraday Cage. That'll certainly -reduce- the
    signal; I don't know if you'd be able to get it down to "no signal"
    at 10 feet.

    Our heavy duty shielding here is aimed more at magnetic fields than
    electric. It's made out of a steel and nickel alloy or something like
    that, and it is *very* expensive.

    I don't have even close to a high enough security clearance to know what
    our our government agents use for signal shielding; the closest I get to
    that is that I know one fellow who will say only that "Yes, I used to work
    for them, and I can't tell you anything about what I did."
     
    Walter Roberson, Jul 20, 2004
    #3
  4. John Larsen

    AG Guest

    Maybe a large iron/steel box like they use for electrical panels would work.
    It might be easier and cheaper in the long run to get a small router and
    just use that instead of the wireless one.
    Here's an idea. Sell the wireless router on Ebay and use the money to buy a
    wired one.
    :)
    AG
     
    AG, Jul 20, 2004
    #4
  5. John Larsen

    Adam Steiner Guest

    Which router are you using? Some (like Linksys) have third party firmware
    which will allow you to do this.
     
    Adam Steiner, Jul 20, 2004
    #5
  6. John Larsen

    Rens Kempen Guest

    :Any suggestions on how to completly block a signal. I have a device

    Lol :) Others would give alot to have a stronger signal and you want to
    competely block it... Buying an UTP router would do I guess.
    I've read about wallpaper that stops radio signals from getting out. It's
    made from the same material as Stealth bombers and is claimed not to be too
    expensive.


    Rens
     
    Rens Kempen, Jul 21, 2004
    #6
  7. Yep, dummy loads. Get a of 50 ohm carbon resistors and remove the
    antenna and replace it with the 50 ohm resistor. Mind you ten feet is
    just this side of, how dumb is this desire?
     
    Michael Erskine, Jul 21, 2004
    #7
  8. Yep, dummy loads. Get a of 50 ohm carbon resistors and remove the
    antenna and replace it with the 50 ohm resistor. Mind you ten feet is
    just this side of, how dumb is this desire?
     
    Michael Erskine, Jul 21, 2004
    #8
  9. Yep, dummy loads. Get a of 50 ohm carbon resistors and remove the
    antenna and replace it with the 50 ohm resistor. Mind you ten feet is
    just this side of, how dumb is this desire?
     
    Michael Erskine, Jul 21, 2004
    #9
  10. Yep, dummy loads. Get a of 50 ohm carbon resistors and remove the
    antenna and replace it with the 50 ohm resistor. Mind you ten feet is
    just this side of, how dumb is this desire?
     
    Michael Erskine, Jul 21, 2004
    #10
  11. What's a "device"? Is that like a wireless router or bridge? If so,
    just configure the MAC address filter to only accept connections from
    one MAC address. Make it one that will never be issued. The result
    is that nobody connects.
     
    Jeff Liebermann, Jul 21, 2004
    #11
  12. John Larsen

    Rens Kempen Guest

    Good solution. Just mind the fact that if someone really wants to get into
    your system, they'll just change their MAC adress (not easy to do, but
    certainly possible).
     
    Rens Kempen, Jul 21, 2004
    #12
  13. John Larsen

    HubSwitch Guest

    Best Idea is repeated in the replies in this thread your asking about, I
    aggree.

    if you cant switch off the wireless

    Use a 50ohm resistor, I am sure if you can obtain one of these and somehow
    get a "spare" antenna you can remove the antenna bit from the spare, and
    solder in the resistor so that it "Shorts" the center pin to the ground
    brass sleeve. This way your wireless has a "Perfect match" and will not
    damage the wireless card..

    Do some googling on Dummy loads and you will understand then about 50ohm and
    75ohm radio transmitters and how they are matched, a dummy load will not
    radiate, apart from miniscule ammounts. esp at 2.4ghz and will be a perfect
    match.

    Opinions by HubSwitch
    (Radio Amateur)
     
    HubSwitch, Jul 21, 2004
    #13
  14. John Larsen

    Barry Jones Guest

    How about using a paper clip for a more permanent solution? :^)
     
    Barry Jones, Jul 21, 2004
    #14
  15. John Larsen

    gary Guest

    Actually, this is by far the best solution offered. The point is that if you
    restrict to a randomly-chosen MAC address that you will never use, an
    outside hacker has no way to know which address you are filtering on.
    Excluding local and group bits, you have 2^46 ~= 64 * 10^12 possibilities, a
    number vastly exceeding any hacker's ability to brute-force.

    Of course, you can also simply configure WEP. Since the OP is not planning
    to use the wireless portion of the network, there will be no wireless
    traffic and therefore no clues to allow hackers to exploit statistical
    weaknesses of WEP. They'd have to brute-force it, and with a keylength of
    128 - 256, that's highly unlikely.

    If you're really obsessive, do both. IMHO, either of these things is
    preferable to yanking antennas and soldering on resistors.
     
    gary, Jul 21, 2004
    #15
  16. The access point does NOT "advertise" or broadcast the available MAC
    addresses that are allowed to connect. It advertises the SSID, it's
    own BSID (MAC address), channel number, modulation method, max speed,
    etc, but not the allowable MAC addresses. If someone wants in, they
    would need some traffic to determine the sole acceptable MAC address,
    and since there would be no traffic to sniff, it could not be
    determined. No traffic means there's nothing to sniff.

    One could mount a brute force attack by sequentially trying every
    possible MAC address (4.3 billion). That would eventually [1] work,
    but would then be faced with cracking the WEP key. Again, without any
    traffic, the WEP key could not be determined by sniffing. If WEP is
    deemed insufficient, one could be devious and use WPA pointing to a
    non-existant RADIUS server, which would never authenticate anyone.

    [1] I just did a very crude measurement on how long it takes for my
    BEFW11S4 takes to respond to a failed association. It varies between
    50msec and 150msec. I'll call it 100msec or 10 MAC addresses per
    second. To try all 4.3billion MAC addresses would take 4,910 days
    with a crude probability of hitting the correct MAC address in about
    half that time.
     
    Jeff Liebermann, Jul 21, 2004
    #16
  17. Just a minor note or two. A short circuit is NOT a perfect match. In
    fact, it's infinite VSWR or as bad a match as an open circuit. The
    prefect match for most wireless cards is 50 ohms. An unterminated
    coax will radiate quite nicely, as will a shorted coax. Terminated
    with 50ohms, it will radiate less, but it's far from zero radiation.

    However, there are few problems with using a 50 ohm terminator.

    1. Finding a 50 ohm terminator in a reverse-SMA or reverse-TNC
    connector is gonna be difficult. When testing radios, I had to make
    my own as none of the vendors had them in stock. When I got weird
    results, I eventually put my home made terminators on the network
    analyzer and found them to be anything but 50 ohms. Finding a 50ohm
    resistor that is still 50 ohms at 2.4GHz is a problem. Building it
    into a connector so that it's part of 50ohm transmission line, is also
    a problem. The best I could do was with a solid wire center pin
    extension, and 4ea 200ohm resistors soldered radially between the
    center wire and the connector shield and that wasn't good enough. So,
    I used a real terminator in an N-connector, and a mess of adapters.

    2. In the DWL-900AP+, there are actually TWO antennas. One goes to
    the outside R-SMA connector and is easily accessible. The other is
    inside the case and is NOT easily accessible. (Note: Internal=left,
    External=right). The two antennas are both active and part of a
    diversity system. You would need to disable the internal antenna in
    the web based setup to make sure it doesn't function.

    3. Even terminated, some radios still radiate quite a bit. I just
    removed the two antennas from my BEFWS11, and installed a pair of
    terminators (actually a pair of 50ohm 6GHz N-Terminators and an N to
    R-TNC adapter). I lose connection with my laptop at about 20ft.
    Longer range testing will require that I put my shoes on and make
    myself presentable.
     
    Jeff Liebermann, Jul 21, 2004
    #17
  18. John Larsen

    John Larsen Guest

    Tried to resist posting exactly why I needed this. Basically I bought
    a WPG54G (wireless presentation gateway) Anyways it definatly has
    issues, guess I should have read the negative reviews before I bought.
    When wired to a connection, or even connecting wirelessly to access
    point then back to wired connection on WPG54G, it works great. When
    directly connecting to it via wireless it works good too, but it
    provides security problems if I allow to you see rest of network
    through it, but I want users to be able to connect to internet and it
    at same time. Seems as though wireless to access point then wired to
    WPG54G would make sence but NOOOOO. Software that comes with it that
    does the VPN stuff to send your screen image into the projector forces
    you to switch your wireless connection to the projector (if it can
    find it that is, if not it stays on your existing network). So thats
    why I want to block it, and 10 feet because laptops would be atleast
    10 feet away as its on the ceiling connected to projector in the
    middle of a ring of tables.
     
    John Larsen, Jul 22, 2004
    #18
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