5 ms·

Is there any knowledge of the mechanism used to hijack the signal, or what WGN/WTTW did to protect against it afterwards? The Wikipedia article seems to indica

Is there any knowledge of the mechanism used to hijack the signal, or what WGN/WTTW did to protect against it afterwards? The Wikipedia article seems to indicate even the engineers never figured it out.

th0ma5 7y ago
I lot of broadcast operations have a frequency that isn't in the broadcast band that they use to send their signal to a remote tower. Presumably if you point a stronger transmission at the receiver you can become the dominant signal. Or at least that's what I always thought. I would think you would have needed some inside information or otherwise have worked in the industry at the time to really pull this off? Maybe not, though.
- xxpor 7y ago
  Every microwave uplink frequency is listed on the the FCC's ULS site: https://www.fcc.gov/wireless/systems-utilities/universal-licensing-system https://www.fcc.gov/wireless/systems-utilities/universal-lic... Usually the uplinks are in the 10+ GHz band, and the antenna (usually looks like a big bass drum on the tower, http://www.steeltowerchn.com/wp-content/uploads/2018/06/Microwave-Antenna-Radio-Tower-GSM-Tower-800x480.jpg http://www.steeltowerchn.com/wp-content/uploads/2018/06/Micr...) is pointed towards the station's studios. So hijacking it would not be trivial. You need to be in the line of site and be able to produce enough power to overwhelm the real signal, which isn't trivial at those frequencies. There's also probably something similar to ATIS to stop unauthorized transmissions. Here's KIRO uplink from their studio to a tower atop Queen Anne Hill in Seattle. The exact location of the transmitter and receiver are in the locations tab. https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=959133 https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKe...
  - 0db532a0 7y ago
    What about 10GHz+ is important to uplink transmission? Better directionality? Harder to spoof?
    - deleted 7y ago
      [deleted]
    - Scoundreller 7y ago
      Smaller antennaes needed for the same gain as lower frequencies. Terrible ability to go through, say, a concrete wall, but that’s an issue for broadcast, not point-to-point. Possibly an advantage by reducing noise from other 10ghz signals (maybe harmonics from a bad microwave oven?). They also have narrower fresnel zones than lower frequencies, so it’s easier to hit your target without having to be too high at both sides. And the usual tradeoffs: Spectrum is available and you want equipment that’s cheap and reliable, but not too cheap either.
      - 0db532a0 7y ago
        Thanks for the info.
  - londons_explore 7y ago
    There is no mention of the read broadcast being overlaid by or fading into the attackers signal, which I would expect if they were pointing an antenna very carefully to maximize their attack. Instead, I think someone physically unplugged a signal cable somewhere and plugged in their own feed. Possibly even an insider.
    - lb1lf 7y ago
      -Just wagering a guess here - the link was probably frequency modulated; an FM receiver has a very strong capture effect - the strongest signal received on the tuned frequency is the only one demodulated; any other, weaker signals are effectively just raising the noise floor.
      - xxpor 7y ago
        Exactly this. This is why planes use AM and not FM so at least you can tell if you're doubling with another station.
        29083011397778 7y ago
        Slight nit-pick: while aircraft primarily use AM, FM is frequently used in services like fire-fighting and forestry. Source: installed FM radios more times than I can count, including troubleshooting one last month
  - lb1lf 7y ago
    > ...hijacking it would not be trivial. You need to be in the line of site and be able to produce enough power to overwhelm the real signal, which isn't trivial at those frequencies. -While power at 10GHz is non-trivial (though significantly less so now than in the eighties!), you can cheat by being closer to the remote tower than the official source, as received power is reduced by the square of the distance from the transmitter.
    - xxpor 7y ago
      That's a good point. I've never really gotten to play with parabolic antennas though, how much would being at the wrong angle affect reception?
      - ldiracdelta 7y ago
        You can find "lobe diagrams" for common antennas. You just look at the angle that the receiving point is at in relation to the transmitting antenna in the lobe diagram.
  - ktm5j 7y ago
    > Every microwave uplink frequency is listed on the the FCC's ULS site: You think that was the case in 1987?
    - xxpor 7y ago
      The information was still available. You might have had to send the FCC a letter though.
  - ISL 7y ago
    What happens when a seaplane flies through that signal path? Does KIRO drop out?
    - xxpor 7y ago
      That's a good question. Thinking of the paths I usually see them take though, I think the beam would always be too low. They'd end up both too close to the tower and too close to the ground.
  - Stratoscope 7y ago
    For anyone interested in this stuff, I highly recommend the KMZ file for Google Earth Pro from: https://www.fccinfo.com/fccinfo_google_earth.php https://www.fccinfo.com/fccinfo_google_earth.php Be sure to get the Google Earth Pro desktop version, not the Chrome version: https://www.google.com/earth/versions/#earth-pro https://www.google.com/earth/versions/#earth-pro The open the KMZ file linked on the fccinfo page above and start exploring! What is neat is that they show you the point to point path for the microwave links. (Select Broadcast Microwave in the sidebar.)

th0ma5 7y ago

I lot of broadcast operations have a frequency that isn't in the broadcast band that they use to send their signal to a remote tower. Presumably if you point a stronger transmission at the receiver you can become the dominant signal. Or at least that's what I always thought. I would think you would have needed some inside information or otherwise have worked in the industry at the time to really pull this off? Maybe not, though.

xxpor 7y ago
Every microwave uplink frequency is listed on the the FCC's ULS site: https://www.fcc.gov/wireless/systems-utilities/universal-licensing-system https://www.fcc.gov/wireless/systems-utilities/universal-lic... Usually the uplinks are in the 10+ GHz band, and the antenna (usually looks like a big bass drum on the tower, http://www.steeltowerchn.com/wp-content/uploads/2018/06/Microwave-Antenna-Radio-Tower-GSM-Tower-800x480.jpg http://www.steeltowerchn.com/wp-content/uploads/2018/06/Micr...) is pointed towards the station's studios. So hijacking it would not be trivial. You need to be in the line of site and be able to produce enough power to overwhelm the real signal, which isn't trivial at those frequencies. There's also probably something similar to ATIS to stop unauthorized transmissions. Here's KIRO uplink from their studio to a tower atop Queen Anne Hill in Seattle. The exact location of the transmitter and receiver are in the locations tab. https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=959133 https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKe...
- 0db532a0 7y ago
  What about 10GHz+ is important to uplink transmission? Better directionality? Harder to spoof?
  - deleted 7y ago
    [deleted]
  - Scoundreller 7y ago
    Smaller antennaes needed for the same gain as lower frequencies. Terrible ability to go through, say, a concrete wall, but that’s an issue for broadcast, not point-to-point. Possibly an advantage by reducing noise from other 10ghz signals (maybe harmonics from a bad microwave oven?). They also have narrower fresnel zones than lower frequencies, so it’s easier to hit your target without having to be too high at both sides. And the usual tradeoffs: Spectrum is available and you want equipment that’s cheap and reliable, but not too cheap either.
    - 0db532a0 7y ago
      Thanks for the info.
- londons_explore 7y ago
  There is no mention of the read broadcast being overlaid by or fading into the attackers signal, which I would expect if they were pointing an antenna very carefully to maximize their attack. Instead, I think someone physically unplugged a signal cable somewhere and plugged in their own feed. Possibly even an insider.
  - lb1lf 7y ago
    -Just wagering a guess here - the link was probably frequency modulated; an FM receiver has a very strong capture effect - the strongest signal received on the tuned frequency is the only one demodulated; any other, weaker signals are effectively just raising the noise floor.
    - xxpor 7y ago
      Exactly this. This is why planes use AM and not FM so at least you can tell if you're doubling with another station.
      - 29083011397778 7y ago
        Slight nit-pick: while aircraft primarily use AM, FM is frequently used in services like fire-fighting and forestry. Source: installed FM radios more times than I can count, including troubleshooting one last month
- lb1lf 7y ago
  > ...hijacking it would not be trivial. You need to be in the line of site and be able to produce enough power to overwhelm the real signal, which isn't trivial at those frequencies. -While power at 10GHz is non-trivial (though significantly less so now than in the eighties!), you can cheat by being closer to the remote tower than the official source, as received power is reduced by the square of the distance from the transmitter.
  - xxpor 7y ago
    That's a good point. I've never really gotten to play with parabolic antennas though, how much would being at the wrong angle affect reception?
    - ldiracdelta 7y ago
      You can find "lobe diagrams" for common antennas. You just look at the angle that the receiving point is at in relation to the transmitting antenna in the lobe diagram.
- ktm5j 7y ago
  > Every microwave uplink frequency is listed on the the FCC's ULS site: You think that was the case in 1987?
  - xxpor 7y ago
    The information was still available. You might have had to send the FCC a letter though.
- ISL 7y ago
  What happens when a seaplane flies through that signal path? Does KIRO drop out?
  - xxpor 7y ago
    That's a good question. Thinking of the paths I usually see them take though, I think the beam would always be too low. They'd end up both too close to the tower and too close to the ground.
- Stratoscope 7y ago
  For anyone interested in this stuff, I highly recommend the KMZ file for Google Earth Pro from: https://www.fccinfo.com/fccinfo_google_earth.php https://www.fccinfo.com/fccinfo_google_earth.php Be sure to get the Google Earth Pro desktop version, not the Chrome version: https://www.google.com/earth/versions/#earth-pro https://www.google.com/earth/versions/#earth-pro The open the KMZ file linked on the fccinfo page above and start exploring! What is neat is that they show you the point to point path for the microwave links. (Select Broadcast Microwave in the sidebar.)