back to article New York mulls terrorist cell phone jamming

New York Police officials are studying whether it's possible to disrupt cell phone communications among terrorists during an attack on the city following reports that gunmen in Mumbai used hand-held devices during a deadly rampage in November. Police Commissioner Raymond Kelly discussed the possible tactic in Washington on …


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  1. Anonymous Coward

    Ready-made trigger mechanism

    If not done right, this could make it nice and easy to detonate a bomb remotely. Simply detect when the mobile network goes down and use that as your trigger.

    Then, plant a bomb, leave the area and report a credible terrorist threat for a nearby part of the city.

    With several devices, you could even set up a synchronised attack. A badly hidden bomb attached to a mobile phone could even serve as the credible threat.

    Anonymous, lest anyone consider this as advice to terrorists.

  2. Charlie Stross

    Here's what I reckon Bruce Schneier will say ...

    In the Mumbai attacks, it was notable that the attackers hit police targets first (including the head of anti-terrorism ops).

    If there's some sort of filter to allow law enforcement officers to register their phones and by-pass a general block on cellphone use, then the <em>first</em> thing any competent attackers will do is whack some cops and take their phones. At which point, the filter becomes more of an impediment to defense than anything else.

  3. Peter Simpson
    Black Helicopters

    Wouldn't it be simpler

    To look at all calls within the period of time of interest, and disallow the suspect phones from the network? That allows police and innocent civilians to continue using the system.

    Should be easy enough to identify the culprits' cells...they would be PAYG, calling the same number or small group of numbers. With the surveillance society currently being developed in the US, I should think this is already being done...

  4. Sillyfellow

    widespread jamming

    i think that widespread jamming would be quite ok under certain circumstances where many are being killed (like what happened recently).

    so some might complain about the (yes, i know.. chaotic) disruption, but when lives are at stake like that then let them complain.

    presumably even satellite phone network operators can block geographic regions also.

    this would also ensure that tech to 'pinpoint' block wouldn't be rampantly misused.

  5. Anonymous Coward

    Ho hum, new tech

    Maybe the NYPD need to ask why they cannot do this already. AXE10 systems have been able to do this for at least a decade. ACOLC

  6. Daniel B.

    SOS Mode

    Hm... if they're *teh law* ... can't they simply make the mobile carriers switch their base stations to "Emergency Calls Only" mode? That cuts off any calls that aren't 911/999/112/080/whatever; so they cut Terry Wrist's comms *and* keep the emergency lines open as well.

  7. Brett Brennan

    Didn't Tom Clancey already cover this?

    In "Rainbow Six", I believe.

    In my poor opinion, this would actually be pretty straight-forward. Assume that you're getting an emergency call BEFORE you shut everything down: you will then have a good geoloc for the incident already. Tapping into the cellular switches gives you a quick picture of what devices are close to the towers covering the terrorist site: you can then proceed to cut inbound service to those areas and simultaneously start back-tracking the calls that were underway and the ownership records for the devices detected. New calls out can be quickly sorted as to destination (hmm, that guy is calling an unlisted number in the hills of Afghanistan...suspicious?).

    Even easier: shut down inbound to all PAYG devices immediately, as those are most likely to be used by terrorists (as well as poor schmucks without credit, but you can't have it all...). The devices with recorded ownership can then be sorted and any attempted calls from them to "unusual" numbers (like three or four people suddenly start calling Afghanistan that have never called further than the Bronx) can be quickly located and handled.

  8. Anonymous Coward
    Black Helicopters

    Already implemented

    Does any place in the US actually have enough capacity for cell phones to keep working during an incident? I had a cellphone for a while and it was pretty much useless.

  9. Charles Manning

    Plans are in the smoking crack stage

    Jamming cell phone signals is not at all easy unless you're prepared to swamp the whole area with very high RF levels that would really pop corn and boil eggs.

    Any RF jamming would not be selective (terrorist signals don't identify themselves with little head scarves) and will jam everyone.

    A much better approach would be to just turn off the cell towers. Kill the comms far more reliably without having to use extra equipment or fill the place with RF.

  10. Mark Allen

    London 7/7/5

    When the tube and buses were bombed in London, they shut down the mobile phone network and turned it into a restricted system. The police, fire, etc have their phone numbers registered so they have priority access during that time.

    I ain't no expert, but that system sounds simple enough to implement in ANY city. Can't be that hard to collect mobile phone numbers of important services who will need access to the network in an emergency.

    I was in London on 7/7/5 and it was funny to see very long queues at every phone box I walked past. :)

  11. Jeremy

    Pointless and probably very expensive.

    If they want to cut cellphones out during an 'attack', why not just erm... Ask/tell the providers to shut down the base stations? Rather a lot cheaper, I suspect.

    Anyway, in such circumstances the population at large do an excellent job of jamming the mobile phone networks through sheer volume of calls and attempted calls.

  12. Chris

    we be jammin'

    "It would also do little to prevent the use of satellite phones."

    Not to mention good old fashioned walkie-talkies, or CB radios, or ham radios, or something built from scratch that transmits on an unlicensed frequency. Then there are smoke signals, signal mirrors, carrier pidgeons, ...

  13. Joe Harrison

    Dare I Say...

    The iPhone could be the saviour of the terrorists?

    3G access and wifi for communication, email is still the best.

    And then to compliment that, google maps... just put a little marker and plant the bomb... GPS does the rest

    I seriously hope that the US government doesn't think that the only way that people from a country full of desert can only communicate via Mobile Phones.

    "Not to mention good old fashioned walkie-talkies, or CB radios, or ham radios, or something built from scratch that transmits on an unlicensed frequency. Then there are smoke signals, signal mirrors, carrier pidgeons, ..."

    Completely agree, apart from making our heads rapidly expand, there's virtually no way to jam all RF in an area, and then you have good 'ol pre-organised plans.

    I recall that people could simply synchronise their watches, and adhere to a timed plan?

    For shame.

  14. Anonymous Coward

    Tsk! Obviously?

    1 - you don't freak out the bad guys as they tend to be freaky enough

    2 - you use triangulation to pinpoint the bad guys

    3 - you use interception conversations to stall or thwart the bad guys

    4 - you don't say to the bad guys "Hey! This is uncle Sam. Put those guns down now or we will suspend your mobile service!"

    5 - you say to the public one thing but not all things?

  15. Henry Wertz Gold badge

    Jamming may be hard.

    "If not done right, this could make it nice and easy to detonate a bomb remotely. Simply detect when the mobile network goes down and use that as your trigger."

    Just don't hook it up through AT&T or your bomb will go off early. *ba-dum-bum* Thank you I'm here all night.

    This kind of jamming would be VERY hard. New York has a very high cell density (in some areas every 1-2 city blocks), the cell could be like 50 feet away from the user so the jammer would have to be pretty powerful to ensure it works. CDMA (and so also WCDMA and UMTS) were designed originally to resist jamming too, which will not help.

  16. Anonymous Coward

    @Joe Harrison

    "there's virtually no way to jam all RF in an area"

    Ever heard of a spark transmitter? Or a cheap badly maintained moped?

    Seriously, spark transmitters will wipe out all realistic RF comms, but require a lot of power to get going (think lightning). Also, they tend to be impulse transmitters, which would have little effect on digital comms with error correction (like GSM/UMTS)

  17. Martin Silver badge

    How to cause panic/chaos

    Reminds me of a story here a few months ago.

    Two US goverment announcements on the same day:

    1, A proposal for an unjammable GPS system in case terrorists tried to cause chaos by jamming GPS signals.

    2. That they would shut down GPS over a city in the event of a terrorist threat so that the terrorists couldn't use it.

  18. Anonymous Coward
    IT Angle

    Of COURSE it's possible

    Vodafone do it every day!

  19. Anonymous Coward
    Anonymous Coward

    Jamming individual devices

    Pay a call-center to constantly ring the phone in question.

    They'll soon turn it off themselves.

  20. Anonymous Coward

    @Ready-made trigger mechanism

    "If not done right, this could make it nice and easy to detonate a bomb remotely. Simply detect when the mobile network goes down and use that as your trigger."

    Surely the trick is not to take the network down completely, use RF jamming or any other Hollywood crap. As all phones have to subscribe to base stations, all base stations are owned by cellphone operators and all cellphone operators are government-friendly, then the friendly government simply prevails upon the cellphone operators only to route calls /to/ specific numbers in a time of emergency.

    In this manner you can make a call /from/ any working phone, but it will only connect if you're calling a pre-approved destination (e.g. emergency services or your neighborhood SWAT team). Robbing a policeman doesn't help as you still can't call your terrorist buddies, and in the event that Officer Dibble's battery runs flat, explodes or expands to several times its size, he need only borrow one from a friendly passer-by.

    It makes the remote-trigger a little harder to program, I guess, as you then have to set the bomb to go bang if it fails to connect to a particular number at a particular time.

    Ah well, back to the drawing board on government money...

  21. Anonymous Coward
    Anonymous Coward

    Wouldn't work

    As someone already mentioned, the terrorists could communicate using a broad range of methods. The most ideal is certainly radio, but even these devices communicate on a broad range of frequencies. The only way to reliably jam their communication would be either a broad-spectrum jammer or one tailored to intelligence gathered at the scene. If the terrorists are smart they'll use police bands and encryption. Obviously using a jammer on those frequencies would be a double-edged sword. Such is life....

  22. Anonymous Coward
    Anonymous Coward

    Shutting down GPS

    "That they would shut down GPS over a city in the event of a terrorist threat so that the terrorists couldn't use it."

    Do you think it's possible to shutdown GPS on a city by city basis??

  23. Anonymous Coward
    Anonymous Coward


    They'll just purchase cheap CB radios for less than £100 each and use those instead.

    Not as great range as using mobile phones but it's probably good enough.

  24. Anonymous Coward
    Black Helicopters

    who's to say ...

    that they don't already have this technology and have out out this story as a smoke screen.

    btw, as far as I remember the Ericsson AXE10 systems are exchanged for fixed line comms and not designed for directly managing mobile phone networks, so yes you could use an AXE10 to cut off a base site, but then you could also do that via various other bits of mobile coms equipment. The other issue is how do you stop the phone hopping to one of the other networks in the area (i.e. if its an international sim). It needs to be coordinated across all the local networks (o2, voda, orange, tmobile, 3 in the uk).

    Blocking ordinary people's phones and not those of the emrgency services also needs those emergency services to get there phones registered, and I bet most phones wouldn't be.

  25. david wilson

    Do terrorists actually need to communicate?

    Even if the attackers in Mumbai *used* phones, would what they did have been impossible, or even significantly harder, without communication?

    They may have used mobiles to some extent, but presumably they had also worked out in advance a reasonable plan of who was to attack what, and in what order. Terrorists holed up in a hotel shooting people didn''t *need* mobile comms to stay where they were and carry on shooting people.

    Even if some perfect system of blocking communications was developed, I don't see how it would stop a similarly-motivated group of people doing basically the same thing again, and as successfully.

    In any case, the authorities wouldn't know there were any coordinated attacks happening until some time after they had started, so communication after brief initial attacks would still be possible whatever system was implemented for emergency control of mobile phones.

  26. Stewart Haywood

    All been thought of before

    All digital mobile standards have provissions for groups or classes of mobiles that are intended to control or limit access. So, limiting network usage to emergency services only over an area is no problem.

    New York needs to talk to the network operators.

  27. norman

    Tin-foil not required

    Of course they need to jam phones during the next terrorist attack, we can't have any more cell phone calls from high jack victims can we?

  28. Herby

    And the season premire of "24" is Sunday evening...

    We can see how all these things are supposed to work in some episode. I'm sure the politicians refer to the TV program for proper methods.

    Oh well. Better luck next time. What did we do before cell phones?

    Try two cans and a piece of string. Works for me!

  29. Dodgy Geezer Silver badge
    Black Helicopters

    Why is it ...

    that the authorities make a lot of noise about brute force actions like blocking all phones?

    When the obvious thing to do is let the 'terrorists' (asuming there are any out there) communicate happily and monitor their messages. For god's sake, so long as the phone is on, you have a radio tag on each 'terrorist'. As well as prior warning of everything they are planning.

    Similarly for things like porn on the net. We should be looking to catch the child abusers who make it, not the saps who look at it. So take resources away from banning it,and put them onto tracing it back to source. There would soon be much less of it around than the current situation, where making it is virtually risk-free.

    I suppose it's a bit much to ask the 'intelligence' services to display a bit of intelligence...

  30. pctechxp

    Shouldn't they follow our example

    and deploy a TETRA network for the emergency services and restrict calls from mobiles to 911 only in these situations to facilitate calls from people trapped etc?

  31. Anonymous Coward

    So many options, so little sense in the idea..

    As has already been pointed out, any properly implemented GSM/PCN system already has the capability to change to a "privileged users only" mode in which pleb to pleb calls don't work (as seen in London on 7/7). This is different from the "network busy" mode seen in any motorway traffic jam or similar unexpectedly large localised group of cellphone users.

    Does that GSM "privileged users only" mode also apply to trendy new 3G networks or are they still largely irrelevant for purposes like this owing to limited coverage?

    Meanwhile, licence-free 446(?)MHz PMR walkie talkies are available untraceably from any number of outlets around Europe at bargain prices, offering maybe a km or so range in the open (albeit no security). For the more adventurous, licenced radio amateur bands on a wide range of frequencies from medium wave to microwave have various possibilities and the relevant kit is relatively widely available though not legitimately usable without a licence (so that should stop the lawbreakers, right?) and again there's no security by default.

    What's the state of play with 27MHz CB these days? That might be another option.

    For a limited setup within or around a small building or buildings, you could use a DECT (digital cordless phone) base station or two and a few DECT handsets, I bet the intelligence folk wouldn't think of checking for that (and the RF side of DECT is relatively secure even if the spooks are listening with a wideband RF monitor; here, shorter range = better security).

    Jamming *all* that lot at the same time over any significant area for any significant number of minutes isn't going to be easy, unless there's an EMP bomb or two handy, and an EMP bomb might just cause more collateral damage than even the Yanks are used to.

    Tricky. Maybe another tactic is necessary.

  32. Eleanor Rigby


    how much does el reg charge for consultancy services? "simply post your questions in article format and have 30 tech experts answer with their best shot". great business model.

  33. James

    UMTS Access Classes

    GPP TS25.304 v3.12.0 and TS22.011 v3.8.0 4.4 describe details of how to determine if emergency calls are allowed in cells using the IE "Access class barred list" which is broadcast in System Information Blocks 3 and 4 (SIB3 and SIB4).

    Network access for emergency calls is controlled by Access class 10. A normal UMTS user equipment (UE) is assigned an access class randomly from 0 to 9; this is stored in the Universal Subscriber Identity Module (USIM). A special UE may also be assigned an access class from 11 to 15, these would typically used by emergency services, network staff, etc (see 22.011 4.2 for details).

    When determining if a typical UE (access class 0 to 9) is allowed to make a normal non-emergency call in a cell, the entry in the "Access class barred list" which corresponds to the access class of the UE is examined. If this indicates the access class is barred, the UE is not allowed to make the call.

    When determining if a typical UE is allowed to make an emergency call in a cell, access class 10 needs to be checked.

    In the case where emergency calls are barred in a cell, is there a need to check access classes 0 to 9 to determine if normal calls are allowed? It would seem reasonable that if emergency calls cannot be connected then all other calls would be barred too.

    Just bar access to calls from specific cells to UE with access class of 0-9.

  34. Anonymous Coward

    Ooo look....

    My Phone uses Wifi as well.

    Ooo look VoIP coonection, primary connection made via VoIP, fail over to PSTN. Receive to WiFi, fail back to PSTN

    So even if they jam the Cells, if I have a Wifi connection, still good chance of getting through...

  35. Anonymous Coward
    Anonymous Coward

    To re-itterate

    As a couple of posters have already noted, jamming is completely unnecessary as there is capability to bar calls from everyone other than authorised emergency users.

    In the UK this is called ACCOLC (Access Overload Control) and was implemented during the 7/7 bombings. The users permitted to use and ACCOLC SIM card is very carefully managed. Generally even front line police officers are not allowed them (presumably because it is assumed that they should be using their TETRA handsets).

    A similar system is also in place on the fixed line network during times of overloading in emergencies where pre-registered numbers are given preference over 'ordinary' phone numbers

    The only downside to ACCOLC is that the Government is somewhat reluctant to implement it as it is then required to compensate mobile companies for lost revenue.

    Using ACCOLC as a method of triggering a detonation would not be effective as it does not jam the network. Handsets can still 'see' the network but calls cannot be connected.

    It surprises me that this was not implemented in Mumbai as I would expect that the mobile network infrastructure would have been relatively modern.

  36. Anonymous Coward
    Anonymous Coward

    And, on a more paranoid note

    You can also use it to make people you don't like go away more easily. How would all those unpleasant videos of police brutality get out with the cell networks down and the person doing the videoing "Indefinately Detained"

  37. Anonymous Coward

    Terror Mode Activated

    This is your phone speaking: Terror mode has been activated. Please put down any weapons and stand by your explosive device of choice. A special squad has been dispatched and will arrive soon. Remember, it's rude to point a gun at someone. Thank you.

  38. druck Silver badge

    A fucking stupid idea

    As mentioned terrorist will easily equip themselves with an alternative radio comms, meanwhile you have cut off the only means of communication available to innocent civilians, which may aid them in getting out of harms way.

  39. Anonymous Coward
    Anonymous Coward

    No title requiered

    A lot of people think its about preventing the enemy to make a plan where ist actually about preventing them from adapting to what the police/anti terror unit does. Any plan no matter how good it is needs to be adjusted as it progresses.

  40. Steve

    Will this really stop terrorists in their tracks?

    Think about it: all the planning is already done, everything is in place, the attack has already begun (the jamming won't start until an attack has been detected). Does anyone really think people (especially those with bombs strapped to their person) who have already started their attack is going to stop? "Hey Mohammed, my phone's stopped working; let's fly home instead" !?!

    No, this won't work at all - I suspect there is a more sinister, in-house reason for this study.

  41. Vladimir Plouzhnikov

    That's so simple.

    Just ban terrorists from using mobile phones.

    That's what would Jacqui Smith do, right?

  42. Dave


    So on the one hand you have a bunch of people who have had loads of time to make as sophisticated as necessary, and may have alternative communications technology.

    On the other hand, you have 'The Authorities' who need to find out what is going on as quickly as possible, and react to the situation as it emerges.

    Finally, you have those caught up in the situation one way or another, and would quite like to escape if/when it is safe to do so.

    Now then, think for a moment, and tell me which of those three groups is going to be LEAST affected by having their communications interrupted?

    Or is this all an elaborate bluff, to try and ensure that future attempts think that there is no point using mobiles phones?

  43. Jon Vandiveer

    NCS or WPS

    Shouldn't be a problem to change the ratio of NCS to unauth users in such a way that only authenticated users could connect to the system

    During emergencies cellular networks can experience congestion due to increased call volumes and/or damage to network facilities, severely curtailing the ability of National Security/Emergency Preparedness (NS/EP) personnel to make emergency calls. With an increasing number of NS/EP personnel relying on cell phones while performing their emergency duties, Wireless Priority Service was developed to provide priority for emergency calls made from cellular telephones.

    Key Federal, State, local, and tribal government, and critical infrastructure personnel are eligible for Wireless Priority Service. Typical users are responsible for the command and control functions critical to management of and response to national security and emergency situations. Wireless Priority Service is an easy-to-use, add-on feature subscribed on a per-cell phone basis; no special phones are required.

    Wireless Priority Service is implemented as software enhancements to cellular networks, and is being deployed by cellular service providers in their coverage areas throughout the United States.

  44. Cortland Richmond

    Radio Silence?

    It appears that NYC may have been reading about the (planned, sued and not carried out) cell-phone jamming demo at a prison last week and gotten the idea that if everyone else could be prevented from talking to each other, the police would enjoy a tactical advantage. However, their plans do not stop at cellular telephones, 2G, 3G or Nth generation; they envision jamming Media feeds so damage assessment isn't available to attackers, and other radio communications that might be used by or exploited by terrorists.

    In the United States that encompasses an astounding array of technologies. Let us start with 3-transistor toy walkie-talkies, CB radios, Family Radio Service, (and the higher power GMRS usually included and illegally used by FRS-buying public), MURS -- a limited channel low VHF service needing no license -- licensed business VHF and UHF, 900 MHz unlicensed Part 15, which includes cordless telephones, 900 MHz exempt (this is a cool radio, frequency hopping and practically indetectible by all but The Black Helicopters). Then add WiFi and its relatives, and 5.8 GHz NII and UWB gadgets. Ham radio too, which at up to 1500 Watts allowed power might be a harder job, though presumably we are considered loyal. (A long superseded US Army manual once listed an increase in Amateur Radio activity as an indication of upcoming guerrilla action.)

    I suspect that technology has advanced beyond any agency's ability to shut down all commmunications. In any case, -- and this is why the prison demo was canceled – it's unlawful in the USA for anyone to make, import, market or sell jammers for communications regulated by the Federal Communications Commission.

    During WW2, when information was needed on what German forces in France were up to, USAF P47's were called in to shoot up telephone wires and force the Jerries onto the wireless. That may be further then the NYPD is willing to go.

    Or is "Speed Limit enforced By Aircraft!" for real?

  45. Anonymous Coward
    Thumb Down

    To defeat a mobile jammer

    use a walkie-talkie, Satellite link, CB radio- or even a directional WiFi link- to get a signal out to a non-jammed area. Then from there have the signal stuck into a pre-placed mobile phone / Wifi connection / etc.

    Alternatively, use the landline phone of the building you're holed up in. Or create a wireless link (ideally directional to prevent anyone from noticing it) to carry a signal to the next building along, a building down the street, etc.

    This is actually a pretty good idea- it'll utterly screw up the plans of the most stupid (so probably most numerous) terrorists, while not screwing up the plans of the more advanced (or better prepared) terrorists.

    Oh, and it doesn't stop people who work alone. Or suicide bombers. Or people who actually have a timed, properly rehearsed plan and stick to it. Or people who are holed up together. Or people who hijack planes and fly them into New York. Or people who release a biological agent / dirty bomb in a subway then walk away.

    You know what, it's not that good an idea. It won't stop anyone except people too thick to spell Terrorist.

  46. Jeremy Wickins


    ... keeping comms open so that the "security" forces know what is happening is good. Mobile phone mikes can be used as eavesdropping devices, so Terry doesn't even have to be making calls! And how accurate is cellphone tracking theses days - a few yards? Basically, when the bad guys are using a device that gives you lots of information, why discourage them?

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