What stops criminals from jamming a channel by sending spoofed signals to its satellite in space, acting like they are from the TV station and therefore hijack or jam the channel?

How can the satellite make sure the receiving signals are actually from the source they are claiming to be?

Do they use some sort of digital signature?

  • Related: GPS spoofing from DefCon 23 youtube.com/watch?v=jwJKMti_aw0
    – Tom K.
    Commented Sep 19, 2018 at 20:03
  • 2
    Usually they don't. The large majority of them are just repeaters, and repeat whatever comes with enough power. What stops criminals is the hefty fines and very high transmitter power required.
    – ThoriumBR
    Commented Sep 19, 2018 at 20:38
  • @ThoriumBR so if the criminals have enough money and equipment then they can easily hijack any channel on a satellite? and how expensive can it get?
    – AlenT
    Commented Sep 20, 2018 at 5:47
  • @AlenT Yes they can, but they would be extremely easy to catch... jamming a TV channel requires quite some noise and you cannot hide it. The same is true with aircraft transponders... they are extremely insecure and attackers could jam signals from airplanes or "fake" the presence of an airplane. However this almost never happens because it's actually easy to figure out the problem and detect its source. Commented Sep 20, 2018 at 7:47
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    @AlenT - please don't keep changing your post. If you have a new but related question, ask it separately, and add a link to this one if needed.
    – Rory Alsop
    Commented Sep 20, 2018 at 8:29

1 Answer 1


Almost every commercial satellite is just a repeater. They have a sensitive receiver and a powerful transmitter, a couple filters, and basically is that. They almost never employ any encryption at all, because sending a computer in the space is expensive, as more weight means more money. And you cannot just send your average Intel processor over, you must design a radiation resistant computer, shield its components with heavy metals (adding weight). So no, just send a repeater.

The security of the satellite is based on the difficulty of interfering with it. Anyone trying to jam a satellite will need a powerful transmitter, a good antenna, and internal knowledge of the receiving band of the satellite. Knowing the frequency is not enough, they need to know the protocol, and that is not just a Google search away. Most of the satellite communication hardware is protected by patents and industrial secrets. They are not usually available.

A radio antenna is not like a laser bean. It radiates on every direction, but with different power levels. It's something called Radiation Pattern. Any good antenna will radiate almost all power in the desired direction, but some power will "leak" around the antenna, even behind it.

Another difficulty is the power level. The power needed depends heavily on the bandwidth. You can send a few bytes per second over a 25mW transmitter to 700km away, but you cannot transmit HDTV to over 35k km on a sub-kW transmitter. And that is expensive and difficult.

So, a transmitter powerful enough to send data over the upper atmosphere to a satellite receiver will leak a lot of power around his antenna, not only on the main frequency, but on the neighbor bands too. That will interfere with the communications of a lot of people - the ham radio operators. And they are professionals, they hate people interfering with their spectrum, and they have knowledge, equipment and motivation to detect the source of the disturbance. Try buying any cheap transmitter on eBay, modify its amplifier to output more power, and let it transmit something for 24h. Someone will knock on your door. Fuming. So don't do that.

So while it's possible, no attackers will do this because:

  • it's very expensive
  • technically difficult
  • getting caught is very easy
  • the fines for doing so are astronomically high
  • and the most important: what would they gain?
  • But how can they get caught? considering the satellite is just a repeater and the company who owns the satellite cannot communicate with the satellite and get info from it to check where the malicious signals are coming from exactly, or can they? if so how?
    – AlenT
    Commented Sep 20, 2018 at 11:45
  • Ham operators around you will notice a huge power spike on some band, triangulate you as a sport (yes, they do unauthorized transmitter finding as a sport), and notify the authorities. Simple as that.
    – ThoriumBR
    Commented Sep 20, 2018 at 11:49
  • but if the criminals are in a country like China and the government is working with them and they jam and hijack a channel, then there is no way the source of it would be known right? how close the "good guys" should be to criminals in order to locate the source?
    – AlenT
    Commented Sep 20, 2018 at 11:53
  • 1
    A criminal in China cannot jam a satellite on the US. The Earth is round (unless some people believe). You must be in view of the satellite, and the receiving antenna must be on a good angle, so you will need to be on the general location of the legit base station.
    – ThoriumBR
    Commented Sep 20, 2018 at 11:57
  • I know that, lets say chinese people have good angle to satellite X and in this TV satellite there are some channels which the government doesn't like (e.g fox news international) but they are not the owner of that satellite, can they hijack some channels or jam them without anyone locating the source? (like doing this in a secluded area) if so, what is the solution to this attack?
    – AlenT
    Commented Sep 20, 2018 at 12:10

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