5 ms·

I always wondered why these things weren't used in prisons. Maybe they are? Here in the UK there is a massive problem with smuggled phones in prisons, and since

by 3chelon 10y ago

I always wondered why these things weren't used in prisons. Maybe they are? Here in the UK there is a massive problem with smuggled phones in prisons, and since by definition their use is illegal in that environment then surely it's OK for law enforcement to jam or even intercept everything? Add to the mix the thick walls and total control of infrastructure and I see no good reason why every illegal phone can't be forced onto a fake network. Legal phones used by staff could be whitelisted.

aembleton 10y ago
Good idea, a pico cell could forward on the calls and SMS from devices with a whitelisted IMSI. Everyone else could just get there's logged and rejected.
- hvidgaard 10y ago
  Just log everything from non whitelisted devices, but let it through and use the intelligence for law enforcement.
mschuster91 10y ago
> I always wondered why these things weren't used in prisons. > Add to the mix the thick walls Because thick walls do not intercept enough of the radio signal. This only works in really remote locations - but e.g. here in Munich there are a number of jails in the city area. If someone would employ a jammer there, the neighbours would protest and/or sue.
- 3chelon 10y ago
  You're probably right about urban prisons. I always think of them as remote but there are plenty in places with very high signal strengths, which would create problems. Low-power pico-cells inside the prison walls could presumably be configured to not cause problems outside. But yes, RF planning is a nightmare and there would doubtless be problems.
MertsA 10y ago
I don't think jamming would really be reasonable in a building. If the walls can contain the jamming signal to their building then the walls will keep out the original signal anyways. I think just RF blocking paint would be a more reasonable solution but this would also interfere with any radios in use by the guards and wouldn't do anything for any prisoners that are outside during the day. Having the cooperation of the cell service providers would be good, you could just have a small pico cell that tries to blackhole any phones in the building but if a prisoner can smuggle in a cell phone then they can probably smuggle in any other handheld radio as well.
- dom0 10y ago
  > RF blocking paint Isn't really a thing. These paints realistically manage 30 dB attenuation at around 1 GHz, which sounds great as a percentage ("99.x% reduction!"), but isn't sufficient to actually deny cellular service. [Paint also normally doesn't cover things like windows etc. which pretty much nullifies them anyway] You can in fact dump a phone into a fridge or freezer, which (at least here) have steel sheets all over them. Phones still get cellular service. What you would need is screen plating and windows with RF screening meshes (and of course special window frames and so on). This is a) extremely expensive b) can manage >60 dB attenuation.
  - lostlogin 10y ago
    With a fridge is the signal perhaps coming in through the door seals? This would make the cage incomplete.
    - oasisbob 10y ago
      Also, any cable that penetrates the "shielding" can make a great antenna unless it's specifically designed not to.
    - deleted 10y ago
      [deleted]
    - deleted 10y ago
      [deleted]
brassic 10y ago
The law in the UK was changed a few years ago to permit this but it wasn't installed because of the cost. A quick search turned up [1] which reckons £300 million for installation and £800,000 per annum to maintain. Which seems a bit pricey. That said, there was a plan to trial it this year, but I can't remember if that was pre- or post-brexit. [1]: http://www.bbc.co.uk/news/uk-england-tyne-35411297 http://www.bbc.co.uk/news/uk-england-tyne-35411297
mig39 10y ago
They were used in Canadian prisons. And it's set off a backlash about broad capture of everyone's communications (including prisoners and employees). http://motherboard.vice.com/read/a-canadian-prison-was-spying-on-people-and-recording-their-calls-and-texts http://motherboard.vice.com/read/a-canadian-prison-was-spyin... http://www.theglobeandmail.com/news/national/opp-launch-criminal-probe-into-use-of-surveillance-device-in-federal-prison/article29240374/ http://www.theglobeandmail.com/news/national/opp-launch-crim...
- apricot 10y ago
  > And it's set off a backlash about broad capture of everyone's communications Oh sweet summer Canadian children.
halomru 10y ago
It's very hard to make sure that the signal extends exactly to the perimeter of the prison. If your jamming signal is weaker, some corners of the prison will have reception. If it's stronger, you are illegally blocking the signal outside your prison. Add to that that signal strength changes with weather, and you have two solutions: either lots of expensive equipment or lots of buffer land owned by the prison. Both are expensive.

by 3chelon 10y ago

aembleton 10y ago

Good idea, a pico cell could forward on the calls and SMS from devices with a whitelisted IMSI. Everyone else could just get there's logged and rejected.

hvidgaard 10y ago
Just log everything from non whitelisted devices, but let it through and use the intelligence for law enforcement.

mschuster91 10y ago

> I always wondered why these things weren't used in prisons. > Add to the mix the thick walls Because thick walls do not intercept enough of the radio signal. This only works in really remote locations - but e.g. here in Munich there are a number of jails in the city area. If someone would employ a jammer there, the neighbours would protest and/or sue.

3chelon 10y ago
You're probably right about urban prisons. I always think of them as remote but there are plenty in places with very high signal strengths, which would create problems. Low-power pico-cells inside the prison walls could presumably be configured to not cause problems outside. But yes, RF planning is a nightmare and there would doubtless be problems.

MertsA 10y ago

I don't think jamming would really be reasonable in a building. If the walls can contain the jamming signal to their building then the walls will keep out the original signal anyways. I think just RF blocking paint would be a more reasonable solution but this would also interfere with any radios in use by the guards and wouldn't do anything for any prisoners that are outside during the day. Having the cooperation of the cell service providers would be good, you could just have a small pico cell that tries to blackhole any phones in the building but if a prisoner can smuggle in a cell phone then they can probably smuggle in any other handheld radio as well.

dom0 10y ago
> RF blocking paint Isn't really a thing. These paints realistically manage 30 dB attenuation at around 1 GHz, which sounds great as a percentage ("99.x% reduction!"), but isn't sufficient to actually deny cellular service. [Paint also normally doesn't cover things like windows etc. which pretty much nullifies them anyway] You can in fact dump a phone into a fridge or freezer, which (at least here) have steel sheets all over them. Phones still get cellular service. What you would need is screen plating and windows with RF screening meshes (and of course special window frames and so on). This is a) extremely expensive b) can manage >60 dB attenuation.
- lostlogin 10y ago
  With a fridge is the signal perhaps coming in through the door seals? This would make the cage incomplete.
  - oasisbob 10y ago
    Also, any cable that penetrates the "shielding" can make a great antenna unless it's specifically designed not to.
  - deleted 10y ago
    [deleted]
  - deleted 10y ago
    [deleted]

brassic 10y ago

The law in the UK was changed a few years ago to permit this but it wasn't installed because of the cost. A quick search turned up [1] which reckons £300 million for installation and £800,000 per annum to maintain. Which seems a bit pricey. That said, there was a plan to trial it this year, but I can't remember if that was pre- or post-brexit. [1]: http://www.bbc.co.uk/news/uk-england-tyne-35411297 http://www.bbc.co.uk/news/uk-england-tyne-35411297

mig39 10y ago

They were used in Canadian prisons. And it's set off a backlash about broad capture of everyone's communications (including prisoners and employees). http://motherboard.vice.com/read/a-canadian-prison-was-spying-on-people-and-recording-their-calls-and-texts http://motherboard.vice.com/read/a-canadian-prison-was-spyin... http://www.theglobeandmail.com/news/national/opp-launch-criminal-probe-into-use-of-surveillance-device-in-federal-prison/article29240374/ http://www.theglobeandmail.com/news/national/opp-launch-crim...

apricot 10y ago
> And it's set off a backlash about broad capture of everyone's communications Oh sweet summer Canadian children.

halomru 10y ago

It's very hard to make sure that the signal extends exactly to the perimeter of the prison. If your jamming signal is weaker, some corners of the prison will have reception. If it's stronger, you are illegally blocking the signal outside your prison. Add to that that signal strength changes with weather, and you have two solutions: either lots of expensive equipment or lots of buffer land owned by the prison. Both are expensive.